Monoclonal antibodies directed to peptide in the context of mhc and methods of making and using monoclonal antibodies

ABSTRACT

Phycoerythrin (PE) and peptide:MHCII (p:MHCII) reactive monoclonal antibodies; methods to generate monoclonal antibodies including, for example, peptide:MHC (p:MHC) reactive monoclonal antibodies; compositions including monoclonal antibodies; and uses thereof.

PRIORITY CLAIM

This application is a continuation of U.S. application Ser. No.15/952,965, filed Apr. 13, 2018 which claims the benefit of U.S.Provisional Application Ser. No. 62/485,762, filed Apr. 14, 2017, whichare incorporated by reference herein in its entirety.

GOVERNMENT FUNDING

This invention was made with government support under AI118635 andAI035296 awarded by the National Institutes of Health. The governmenthas certain rights in the invention.

SEQUENCE LISTING

This application contains a Sequence Listing submitted electronically,in a file entitled “56939CON1_Seqlisting.XML” having a size of 43,763kilobytes and created on Jan. 23, 2023 which is incorporated byreference herein.

BACKGROUND

The first monoclonal antibody (MAb) reactive to a defined proteinantigen was reported in 1975 (Kohler and Milstein, Nature 256, 495-497(1975)). The utility and broad use of MAbs in biological systems earnedKohler and Milstein the Nobel Prize for medicine in 1984. But thegeneration of MAbs that target peptide in the context of MHCII has onlyoccurred a few times since 1975. (Murphy et al. Nature 338:765-768(1989); Zhang et al. Proc Natl Acad Sci USA 111:2656-2661 (2014); Wolplet al. Tissue Antigens 51, 258-269 (1998); Muraille et al. PLoSpathogens 6:e1001154 (2010); Baldwin et al. J Exp Med 189, 13-24 (1999);Zhong et al. Proc Natl Acad Sci U SA 94:13856-13861 (1997); Dadaglio etal. Immunity 6, 727-738 (1997).)

To generate a MAb using the traditional approach, mice are immunized,the responding B cells are isolated, fused to myeloma cells withhypoxanthine-aminopterin-thymidine (HAT) based selection, screened andsub-cloned to isolate monoclonal hybridomas (Yokoyama et al. Curr ProtocImmunol 102, Unit 25 (2013)). Screening requires the examination ofhundreds or even thousands of clones for one MAb, creating a majorbottleneck. This approach typically yields fewer than 1 percent (%)hybridomas specific for a protein target antigen causing a prominenthurdle, both in time and resources. Moreover, this traditional approachis not specifically designed to generate peptide:MHC (p:MHC) reactiveMAbs, and B cell tolerance against self-MHC adds to the difficulty ofgenerating p:MHC reactive MAbs.

SUMMARY OF THE INVENTION

This disclosure describes phycoerythrin (PE) and peptide:MHCII (p:MHCII)reactive MAbs and methods to generate monoclonal antibodies including,for example, peptide:MHC (p:MHC) reactive MAbs.

In one aspect, this disclosure describes a method including: immunizinga subject with a composition including an antigen; isolating apopulation of cells from the subject; enriching a subpopulation of cellsfrom the population of cells; and forming a hybridoma from a cellselected from the subpopulation of cells.

In some embodiments, the antigen includes a peptide-MHC complex (p:MHC),and enriching a subpopulation of cells includes excluding cells that donot bind to p:MHC. In some embodiments, the antigen includes a monomericpeptide-MHC complex. In some embodiments, the antigen includes at leasttwo peptide-MHC complexes. Each peptide-MHC complex may include the sameMHC, but the peptide of each peptide-MHC complex may be different. Insome embodiments, the antigen includes a peptide-MHC Class I complex(p:MHCI) or a peptide-MHC Class II complex (p:MHCII). In someembodiments, the method includes immunizing a subject with a compositionincluding an antigen including one peptide-MHC complex and subsequentlyimmunizing the subject with a composition including an antigen includinganother peptide-MHC complex.

In some embodiments, excluding cells that do not bind to p:MHC includesexcluding cells that bind to a peptide not bound to an MHC complexand/or to an MHC complex not bound to a peptide.

In some embodiments, enriching a subpopulation of cells includesenriching a subpopulation of cells capable of binding to a multimericform of the antigen. The multimeric form of the antigen may include atleast one of a biotin, a desthiobiotin, and a fluorescent biotinderivative. When a multimeric form of the antigen includes at least oneof a marker and a photosynthetic pigment, excluding cells that do notbind to p:MHC may include excluding cells that bind to the marker or thephotosynthetic pigment.

In some embodiments, enriching a subpopulation of cells includesexcluding cells that bind to a second peptide-MHC complex, wherein thesecond peptide-MHC complex includes the same MHC complex as the p:MHC ofthe antigen used to immunize the subject, and further wherein the secondpeptide-MHC complex includes a different peptide than the p:MHC of theantigen used to immunize the subject.

In some embodiments, enriching the subpopulation of the cells includesusing flow cytometric identification and/or sorting.

In some embodiments, enriching a subpopulation of cells further includesat least one of increasing the proportion of B cells in the populationthat bind the antigen, identifying expression of a lymphocyte marker,identifying mononuclear cells, identifying expression of a B cellmarker, testing for viability, and testing for antigen specificity.

In some embodiments, the composition including an antigen furtherincludes an adjuvant. When the composition includes an adjuvant,excluding cells that do not bind to p:MHC may include excluding cellsthat bind to the adjuvant.

In some embodiments, the method further includes screening the hybridomafor production of an antibody specific for the p:MHC.

In some embodiments, the subject is a mammal including, for example, amouse, a humanized mouse, a rat or a rabbit.

In another aspect, this disclosure describes a monoclonal antibody. Insome embodiments, the monoclonal antibody includes a heavy chainvariable region of FS1, W6, or XRI1 and/or a light chain variable regionpolypeptide sequence of FS1, W6, or XRI1. In some embodiments, themonoclonal antibody includes a heavy chain variable region as disclosedin FIG. 23 and/or a light chain variable region polypeptide sequence asdisclosed in FIG. 23 .

In some embodiments, the monoclonal antibody includes a heavy chainvariable region including a CDR of FS1, W6, or XRI1 and/or a light chainvariable region including a CDR of FS1, W6, or XRI1. In someembodiments, the monoclonal antibody includes a heavy chain variableregion including a CDR as disclosed in FIG. 23 and/or a light chainvariable region including a CDR as disclosed in FIG. 23 .

In a further aspect, this disclosure describes methods of using themonoclonal antibodies described herein.

The term “antibody” as used herein refers to a molecule that contains atleast one antigen binding site that immunospecifically binds to aparticular antigen target of interest. The term “antibody” thus includesbut is not limited to a full length antibody and/or its variants, afragment thereof, peptibodies and variants thereof, monoclonalantibodies (including full-length monoclonal antibodies), polyclonalantibodies, multispecific antibodies (e.g., bispecific antibodies)formed from at least two intact antibodies, human antibodies, humanizedantibodies, and antibody mimetics that mimic the structure and/orfunction of an antibody or a specified fragment or portion thereof,including single chain antibodies and fragments thereof. Binding of anantibody to a target can cause a variety of effects, such as but notlimited to where such binding modulates, decreases, increases,antagonizes, agonizes, mitigates, alleviates, blocks, inhibits,abrogates and/or interferes with at least one target activity orbinding, or with receptor activity or binding, in vitro, in situ, and/orin vivo. The present disclosure, thus, encompasses antibody fragmentscapable of binding to a biological molecule (such as an antigen orreceptor) or portions thereof, including but not limited to Fab, Fab′and F(ab′)₂, pFc′, Fd, a single domain antibody (sdAb), a variablefragment (Fv), a single-chain variable fragment (scFv) or adisulfide-linked Fv (sdFv); a diabody or a bivalent diabody; a linearantibody; a single-chain antibody molecule; and a multispecific antibodyformed from antibody fragments. The antibody can be of any type (e.g.,IgG, IgE, IgM, IgD, IgA and IgY), class (e.g., IgG1, IgG2, IgG3, IgG4,IgA1 and IgA2), or subclass.

The term “monoclonal antibody” as used herein refers to an antibodyobtained from a population of substantially homogeneous antibodies, thatis, the individual antibodies comprising the population are identicalexcept for possible naturally occurring mutations that may be present inminor amounts. Monoclonal antibodies are highly specific, being directedagainst a single antigenic site. Furthermore, in contrast to polyclonalantibody preparations which typically include different antibodiesdirected against different determinants (epitopes), each monoclonalantibody is directed against a single determinant on the antigen. Themonoclonal antibodies can be synthesized by hybridoma cellsuncontaminated by other immunoglobulin producing cells. Alternatively,the monoclonal antibody can be produced by cells stably or transientlytransfected with the heavy and light chain genes encoding the monoclonalantibody.

The modifier “monoclonal” indicates the character of the antibody asbeing obtained from a substantially homogeneous population ofantibodies, and is not to be construed as requiring engineering of theantibody by any particular method. In some embodiments, the term“monoclonal” is used herein to refers to an antibody that is derivedfrom a clonal population of cells, including any eukaryotic,prokaryotic, or phage clone, and not the method by which the antibodywas engineered.

As used herein, “isolated” refers to material removed from its originalenvironment (e.g., the natural environment if it is naturallyoccurring), and thus is altered “by the hand of man” from its naturalstate.

As used herein “in vitro” is in cell culture and “in vivo” is within thebody of a subject.

As used herein “sequence identity” between two polypeptides isdetermined by comparing the amino acid sequence of one polypeptide tothe sequence of a second polypeptide. When discussed herein, whether anyparticular polypeptide is at least 40 percent (%), at least 45%, atleast 50%, at least 55%, at least 60%, at least 65%, at least 70%, atleast 75%, at least 80%, at least 85%, at least 90%, at least 95%, atleast 96%, at least 97%, at least 98%, or at least 99% identical toanother polypeptide can be determined using methods and computerprograms/software known in the art such as, but not limited to, theBESTFIT program (Wisconsin Sequence Analysis Package, Version 8 forUnix, Genetics Computer Group, University Research Park, 575 ScienceDrive, Madison, Wis. 53711). BESTFIT uses the local homology algorithmof Smith and Waterman, Advances in Applied Mathematics 2:482-489 (1981),to find the best segment of homology between two sequences. When usingBESTFIT or any other sequence alignment program to determine whether aparticular sequence is, for example, 95% identical to a referencesequence according to the present invention, the parameters are set, ofcourse, such that the percentage of identity is calculated over the fulllength of the reference polypeptide sequence and that gaps in homologyof up to 5% of the total number of amino acids in the reference sequenceare allowed.

Herein, “room temperature” is 62° F. to 78° F. or, more preferably, 65°F. to 75° F.

The words “preferred” and “preferably” refer to embodiments of theinvention that may afford certain benefits, under certain circumstances.However, other embodiments may also be preferred, under the same orother circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the invention.

The terms “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims.

Unless otherwise specified, “a,” “an,” “the,” and “at least one” areused interchangeably and mean one or more than one.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.).

For any method disclosed herein that includes discrete steps, the stepsmay be conducted in any feasible order. And, as appropriate, anycombination of two or more steps may be conducted simultaneously.

Unless otherwise indicated, all numbers expressing quantities ofcomponents, molecular weights, and so forth used in the specificationand claims are to be understood as being modified in all instances bythe term “about.” Accordingly, unless otherwise indicated to thecontrary, the numerical parameters set forth in the specification andclaims are approximations that may vary depending upon the desiredproperties sought to be obtained by the present invention. At the veryleast, and not as an attempt to limit the doctrine of equivalents to thescope of the claims, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. All numerical values, however, inherently contain a rangenecessarily resulting from the standard deviation found in theirrespective testing measurements.

All headings are for the convenience of the reader and should not beused to limit the meaning of the text that follows the heading, unlessso specified.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the MHC II peptide sequence groove position of two T cellactivating mimotopes, peptide 31 (p31) (SEQ ID NO:6) and peptide 63(p63) (SEQ ID NO:5), and WE14, a cleavage product of Chromogranin A (SEQID NO:16).

FIG. 2A shows an immunization and antigen-specific boost scheme togenerate a cross-reactive monoclonal antibody using bound peptide 31(p31)-IA^(g7) monomer in complete Freund's adjuvant (CFA) and peptide 63(p63)-IA^(g7) monomer. FIG. 2B shows an exemplary bound peptide-MHCII(p:MHCII) monomer tagged with biotin and 6× His.

FIG. 3 shows magnetic enrichment and isolation of antibody-expressingcells produced according to the immunization scheme of FIG. 2 . Briefly,a single cell suspension was made from splenocytes and cells from pooledlymph nodes (inguinal, brachial, cervical and axillary) from theimmunized animal, and cells were labeled with a phycoerythrin(PE)-conjugated peptide:MHCII tetramer. After washing, cells werelabeled with anti-PE microbeads, and a magnetic column system was usedto enrich and isolate antibody-expressing cells bound to the microbeads.

FIG. 4 shows a representative cross-reactive ELISA result showing thatan antibody produced according to the methods of Example 1 wascross-reactive to p31:IA^(g7) and p63:IA^(g7).

FIG. 5 shows an isotype analysis of antibodies produced according to themethods of Example 1.

FIG. 6 shows an exemplary scheme for the generation and validation ofp:MHCII MAb. As further described in Example 2, mice were immunized withp:MHCII emulsified in complete Freund's adjuvant (CFA). To validatesuccessful priming and expansion, the phenotype of p:MHCII-specific Bcells in naïve mice was compared to the phenotype on day 7 postimmunization. After 7 days, splenocytes from naïve and immunized micewere collected and stained for specific immunogen p:MHCII-PE and decoyp:MHCII APC, streptavidin-PE-AF647, streptavidin-APC-DyLight 755,magnetically enriched using anti-PE and anti-APC magnetic beads andanalyzed by flow cytometry (Taylor et al. J. Exp. Med. 209:2065-2077(2012)). p:MHCII-specific B cells were gated from streptavidin, APC andPE binding cells (Taylor et al. J. Exp. Med. 209:2065-2077 (2012).Germinal center B cells (GL7⁺ and Intracellular Ig) and plasma cells(GL7⁻ and intracellular Ig⁺) were then identified from the variousB-cell populations binding these distinct tetramer reagents todemonstrate successful priming. After 28 days, mice were boosted with asecond immunization of p63:IA^(g7) monomeric protein intravenously.Three days following the immune boost, magnetic B-cell enrichment forsplenic B cells binding to the p63:IA^(g7) tetramer:PE reagent wereperformed. Enriched cells were fused with myeloma fusion partners,expanded and screened for in vitro and in vivo validation.

FIG. 7 (A-B) shows enrichment and phenotypic analysis ofp:MHCII-specific B cells of Example 2. FIG. 7A shows flow cytometricanalysis of p:MHCII-specific B cells before and 7 days post-immunizationwith p:MHCII monomer. Splenocytes from naïve and immunized mice werecollected and stained for specific immunogen p:MHCII-PE and decoyp:MHCII APC tetramers and magnetically enriched using anti-PE andanti-APC magnetic beads. Germinal center B cells (GL7⁺ and IntracellularIg) and plasma cells (GL7⁻ and intracellular Ig⁺) were then identifiedfrom the various p:MHCII-specific B-cell populations binding thesedistinct tetramer reagents. p:MHCII-specific B cells were gated fromstreptavidin, APC and PE binding cells using SA-APC-DyLight 755 orSA-PE-AF647 20. FIG. 7B shows a representative flow cytometric analysisof p63:IA^(g7)-enriched antigen-specific B cells obtained before myelomafusion. Germinal center B cells (GL7⁺ and Intracellular Ig⁻) and plasmacells (GL7⁻ and intracellular Ig⁺) were then identified within thep63:IA^(g7)-PE tetramer specific B cells. Data are representative of twoindependent experiments with 2-5 mice per group.

FIG. 8 (A-E) shows screening and functional validation of the FS1 MAb.FIG. 8A shows ELISA results from twenty independent hybridomas presentedas percent maximum absorbance compared to anti-IA^(g7) mouse hybridomaclone 10-2.16 as positive control. Plates were coated with p63:IA^(g7)monomer and compared to InsB₉₋₂₃:IA^(g7) monomer-coated plates.Supernatant was added and secondary antibody was used to measure bindingby ELISA. Media alone was used for a negative control (dashed line).FIG. 8B shows carboxyfluorescein succinimidyl ester (CFSE) proliferationin response to p63 peptide. The assay was performed using splenocytesfrom BDC2.5 mice. The percent of divided CD4⁺ T cells is shown withmaximum division with peptide alone (87.5%) and inhibition with eachhybridoma supernatant screened. Data are representative from twoindependent experiments. FIG. 8C shows the effect of culturingCFSE-labelled BDC2.5 T cells for 4 days in the presence of p63 or p31peptide with varied concentrations of FS1 MAb or isotype control IgG1antibody (1.72 mM). The percent divided CD4⁺ T cells is shown for eachconcentration of blocking FS1 MAb compared with maximum proliferationwith no antibody (no Ab) or isotype Ab (top panel). FS1 MAb effects onIFNγ cytokine production from the cultured cells (middle panel) andIL-17A cytokine production (bottom panel) are also shown. Data arerepresentative of two independent experiments in duplicate for eachantigen concentration. FIG. 8D shows in vitro antibody staining onantigen-presenting cells following peptide pulse with p63 or OVA₁₄₁₋₁₆₀using purified clone FS1 MAb to detect p63 loaded conventional dendriticcells (cDCs) (CD8α⁺, CD11c⁺, MHCII⁺, CDR⁻, F4/80⁻), and B cells (B220⁺,MHCII⁺, CD11c⁻, CD3ε⁻, F4/80⁻) but not CD4⁺ or CD8⁺ T cells (CD3ε⁺,CD11c⁻, CD11b⁻, B220⁻, F4/80⁻) compared with no p63 peptide negativecontrol. Data are representative of three independent experiments. FIG.8E shows in vivo staining of antigen-presenting cells with FS1 MAbfollowing footpad immunization. NOD mice received p63 or OVA₁₄₁₋₁₆₀peptide and 1.5 hours following injection the popliteal lymph node wascollected and stained for antigen-specific presentation usingbiotinylated FS1 MAb. FS1 MAb staining was detected on DCs and B cells,but not T cells using fluorochrome-linked streptavidin. Statisticalsignificance was calculated using a two-tailed Student's t-test. Dataare representative from two independent experiments with 2-4 mice pergroup.

FIG. 9 (A-C) shows functional validation of W6 (2W:IA^(b)) MAbs. FIG. 9Ashows in vitro antigen presentation on bone marrow-derived dendriticcells isolated from C57BL/6 mice. Cells were stained with W6 MAb after24 hours pulse with GFP covalently linked to 2W peptide. GFP and W6 MAbdouble-positive cells are shown compared to isotype control (insert).Data are representative of two independent experiments with 3 mice pergroup. FIG. 9B shows in vivo immunostaining of 2W antigen-presentingcells. Mice were immunized intradermally in the ear with eitherovalbumin (OVA) or 2W-GFP. 24 hours post immunization, cervical lymphnodes were collected, dissociated and gated for lymphocyte size,singlets, CD19⁻ and MHCII⁺. Statistical significance was calculatedusing a two-tailed Student's t-test. Data are representative of twoindependent experiments with four animals per group. FIG. 9C showspercentages of CD19⁻, CD11b⁺, CD11c⁺ dendritic cells in mice immunizedwith 2W-GFP and either CpG or dmLT (Norton et al. Vaccine 33:1909-1915(2015)) assayed using W6 MAb. Twenty-four hours after immunization,draining lymph nodes were assayed using W6 MAb. Data are representativeof four independent experiments with 2-3 mice per group.

FIG. 10 (A-B) shows in vivo blockade of T-cell proliferation andprevention of T-cell tolerance following FS1 administration. FIG. 10Ashows in vivo blockade of antigen-specific proliferation and cell cycleprogression 4 days after intravenous (i.v.) administration of FS1 MAbplus p63 and LPS compared to Y-Ae (anti-IEα:IA^(b)), control treatmentor untreated naïve mice. p63:IA^(g7) tetramer PE and APC double positivecells from the spleen were enriched and gated on lymphocyte size,singlets, live cells, B220⁻, CD11c⁻, CD11b⁻, CD3ε⁺, and CD4⁺.Statistical significance was calculated using a two-tailed Student'st-test. Data are representative of two independent experiments with 2-3mice per group. FIG. 10B shows in vivo blockade of antigen-specifictolerance using FS1 MAb to prevent ethylene-carbodiimideantigen-fixed-coupled cell tolerance. NOD mice received activated BDC2.5TCR transgenic CD4⁺ T cells to induce diabetes. Ten mice per groupreceived either p63-coupled cells or BSA-coupled cells. Five mice pertreatment received FS1 MAb or control. Mice were followed daily fordiabetes after day 3 by blood glucose measurements. Data arerepresentative of two independent experiments.

FIG. 11 (A-C) shows in vivo blockade of T-cell proliferation andprevention of bacterial clearance following W6 administration. FIG. 11A.C57BL/6 mice were infected with Listeria monocytogenes expressing 2W.Seven days post infection and W6 antibody treatment, 2W-specific cellswere magnetically enriched from the spleen. Cells were gated onlymphocyte size, singlets, CD19⁻, F4/80⁻, CD11c⁻, CD11b⁻, CD3ε⁺, andCD4⁺. Shown are representative FACS plots for CD44^(hi) versus 2W:IA^(b)tetramer PE⁺ cells and fold expansion of antigen-specific cells relativeto uninfected mice. Data are representative of two independentexperiments with 3-5 mice per group. FIG. 11 (B-C). Wild type 129 S1mice were infected with Salmonella Typhimurium expressing 2W, and 14days following infection mice were treated with blocking W6 MAb. FIG.11B. At day 35 post infection (21 days following MAb administration),the number of 2W-specific T cells was determined from the spleen asdescribed in FIG. 11A. FIG. 11C. At day 35 post infection (21 daysfollowing MAb administration), the colony forming units for the spleenwere determined. Statistical significance was calculated using atwo-tailed Student's t-test. Data include 10 mice from two independentexperiments.

FIG. 12 shows a flow cytometry gating strategy used in Example 3.

FIG. 13 shows a flow cytometry gating strategy used in Example 3.

FIG. 14 shows indirect ELISA screening of hybridoma supernatants asdescribed in Example 3.

FIG. 15A shows an exemplary immunization scheme as used in Example 4.FIG. 15B shows an exemplary scheme for the generation and validation ofp:MHCII MAb as used in Example 4.

FIG. 16 shows IA^(g7) groove position for InsB:9-23(wt) (SEQ ID NO:17),InsB:9-23 p8E (SEQ ID NO:9), and InsB:9-23 p8G (SEQ ID NO:18).

FIG. 17 (A-B) shows validation of p:MHCII tetramers for B cell pulldown.NOD mice were immunized with 10 μg of InsB p8E:IA^(g7) in CFA. After 14days, secondary lymphoid organs were dual tetramer stained with InsBp8E:IA^(g7)-PE and p31:IA^(g7)-APC. FIG. 17A. InsB p8E:IA^(g7) tetramerpositive cells were gated on lymphocytes, singlets, dump-, Ig(H+L) orB220+, SA-PE*AF647 and SA-APC*dyl755- and decoy p31:IA^(g7)-APC-. FIG.17B. After pre-incubation with 16.5 μM 96% of InsB p8E:IA^(g7) tetramerbinders were competed off while only 40% of p31:IA^(g7) binders werecompeted off.

FIG. 18 (A-C) shows in vitro staining of Ins 4G8 hybridoma with IA^(g7)tetramers. FIG. 18A and FIG. 18B show Ins 4G8 hybridomas bind both InsBp8G:IA^(g7) and InsB p8E:IA^(g7) tetramers.

FIG. 18C shows Ins 4G8 hybridomas bind HEL:IA^(g7) and hCLIP:IA^(g7)with much lower affinity than p8G:IA^(g7) and InsB p8E:IA^(g7)tetramers.

FIG. 19 (A-D) shows in vitro staining of peptide pulsed bone marrowderived dendritic cells (BMDCs) with XRI1 directly conjugated to AF647.Bone marrow was harvested and cultured for 9 days in 20 ng/mL GM-CSF.BMDCs were pulsed overnight with 40 μM peptide or no peptide+1 μg/mL LPSand then stained with AF-647-XRI1. FIG. 19A. B6.G7 BMDCs were pulsedwith InsB p8E, InsB p8G or irrelevant peptides and AF647-XRI1 stainingwas measured FIG. 19B. The geometric mean (gMFI) of the AF647-XRI1staining of FIG. 19A was determined. FIG. 19C. BMDCs from NOD, B6, B6.G7and various NOD IA^(g7) knockouts were pulsed with InsB p8E andAF647-XRI1 staining was measured. FIG. 19D. The gMFI of the AF647-XRI1staining of FIG. 19C was determined.

FIG. 20 (A-D) shows in vivo validation of XRI1. NOD mice were injectedi.p. (intraperitoneally) with 20 μg of either InsB p8E or InsB p8G+50 μgLPS and 500 μg of XRI1 (4G8) or isotype control antibody on day 0 and500 μg of XRI1 (4G8) or isotype control antibody for a second dose onday +2. Five days later (day 7 after priming), secondary lymphoid organswere collected and dual tetramer staining was performed followed by MACSanti-APC and anti-PE enrichment. Tetramer positive T cells were gated onlymphocytes, single cells, dump-, CD3⁺, CD4⁺, dual tetramer⁺.Representative flow cytometry analysis of CD4 T cell expansion afterInsB p8E (FIG. 20A) or InsB p8G (FIG. 20B) peptide stimulation withisotype control antibody treatment at days 0 and 2 (left panels of FIG.20A and FIG. 20B) or XRI1 (4G8) treatment at days 0 and 2 (right panelsof FIG. 20A and FIG. 20B). FIG. 20C shows quantification of tetramerpositive cells of naïve mice compared to mice immunized withpeptide+LPS+Isotype control or peptide+LPS+XRI1 treatment for InsB p8E.InsB p8G, or p63 tetramers. FIG. 20D. Frequency of CD44 high PD-1⁺ cellswithin the tetramer⁺ CD4 gate. N=2-3.

FIG. 21 shows heavy chain XRI1 DNA (SEQ ID NO:1) and protein (SEQ IDNO:2) sequences (produced by clone Ins 4G8).

FIG. 22 shows light chain XRI1 DNA (SEQ ID NO:3) and protein (SEQ IDNO:4) sequences (produced by clone Ins 4G8).

FIG. 23 shows light chain and heavy chain DNA and protein sequences forthe antibodies produced by clones of FIG. 14 . FIG. 23A shows the lightchain DNA sequence (SEQ ID NO:19), the light chain protein sequence (SEQID NO:20), the heavy chain DNA sequence (SEQ ID NO:21), and the heavychain protein sequence (SEQ ID NO:22) of the antibody produced by Clone1 of FIG. 14 . FIG. 23B shows the light chain DNA sequence (SEQ IDNO:23), the light chain protein sequence (SEQ ID NO:24), the heavy chainDNA sequence (SEQ ID NO:25), and the heavy chain protein sequence (SEQID NO:26) of the antibody produced by Clone 4 of FIG. 14 . FIG. 23Cshows the light chain DNA sequence (SEQ ID NO:27), the light chainprotein sequence (SEQ ID NO:28), the heavy chain DNA sequence (SEQ IDNO:29), and the heavy chain protein sequence (SEQ ID NO:30) of theantibody produced by Clone 5 of FIG. 14 .

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

This disclosure describes phycoerythrin (PE) and peptide:MHCII (p:MHCII)reactive MAbs and methods to generate monoclonal antibodies including,for example, peptide:MHC (p:MHC) reactive MAbs.

The monoclonal antibodies described herein recognize an antigen. In someembodiments, the antigen may include a peptide and/or a hapten. In someembodiments, the peptide and/or hapten may be conjugated to a carriermolecule. In some embodiments, the monoclonal antibodies describedherein preferably recognize a peptide-MHC complex.

In some embodiments, the antigen may include a foreign antigen (e.g., abacterial and/or viral antigen from an infected cell), an allogeneicantigen (e.g., an antigen recognized after transplantation), a tumorneo-antigen, and/or a self-antigen (e.g., a self-protein targeted duringautoimmunity).

In some embodiments, the monoclonal antibodies described herein mayrecognize an antigen that includes a peptide-MHC complex (also referredto herein as peptide:MHC and/or p:MHC). In some embodiments, apeptide-MHC complex may include a foreign peptide. In some embodiments,a peptide-MHC complex may include an allogeneic peptide. In someembodiments, a peptide-MHC complex may include a self peptide. In someembodiments, a peptide-MHC complex may include a hybrid self-peptide. Insome embodiments, a peptide-MHC complex may include a tumor antigen or atumor neo-antigen.

In some embodiments, the MHC complex may be an MHC Class I complex. Insome embodiments, the MHC complex may be an MHC Class II complex. Insome embodiments, the MHC complex may be mammalian. In some embodiments,the mammal may include a human, a mouse, a dog, a rabbit, a non-humanprimate, a sheep, a cat, a horse, a cow, a chicken, etc. In someembodiments, the MHC complex may be non-mammalian including, forexample, from an amphibian or a reptile. In some embodiments, the MHCcomplex may be human. For example, a human MHC Class I complex mayinclude HLA-A, HLA-B, or HLA-C; a human MHC class II complex may includeHLA-DP, HLA-DM, HLA-DOA, HLA-DOB, HLA-DQ, or HLA-DR. In someembodiments, the MHC complex may be murine. For example, a murine MHCClass I complex may include H-2D, H-2K, H-2L, H-2Q, H-2M, or H-2T. Forexample, a murine MHC Class II complex may include H-2A, H-2E, H-2M, orH-2O. Murine MHC may further include a haplotype. (See, e.g., KubyImmunology, 4^(th) Ed., 2000, Chapter 7 (providing a general descriptionof MHC complexes in humans and mice); Mouse Alloantigens, BioLegendResource page, available on the world wide web atbiolegend.com/media_assets/support_resource/BioLegend_Mouse_Alloantigens.pdf(providing commonly used laboratory mouse haplotypes and alloantigens).)

In some embodiments, including when the antigen includes a peptide-MHCcomplex, the peptide may be covalently linked to the MHC complex.

In some embodiments, an algorithm may be used predict peptide registerbinding leading to selection of p:MHC for use as an antigen. (See, e.g.,Muraille et al. PLoS pathogens 6:1001154 (2010).)

In some embodiments, high throughput generation may be used to producep:MHC monomers by peptide exchange (Day et al. J Clin Invest 112:831-842(2003)).

In some embodiments, as described, for example, in Example 1, theantigen may include a peptide-MHC complex including p31:IA^(g7) and/orp63:IA^(g7). In an exemplary embodiment, as described, for example, inExample 2, the antigen may include a peptide-MHC complex includingp31:IA^(g7) or 2W:IA^(b). As described, for example, in Examples 2 and4, the antigen may include a peptide-MHC complex including p8G:IA^(g7)or p8E:IA^(b). In some embodiments, the peptide-MHC complex may includea cross reactive peptide MHC target. In some embodiments, thepeptide-MHC complex may be specific for a single peptide:MHC target.

In some embodiments, as described, for example, in Example 1, theantigen may include phycoerythrin (PE).

The need for immunotherapeutics in the form of MAbs directed againstp:MHCII is expected to increase as new pathways and novel antigens areidentified during disease. As these targets are identified, there willbe a great need to limit antigen specific T cell responses and themethodology described here may dramatically improve this capability overconventional methods.

In some embodiments, a method of making a monoclonal antibody asdescribed herein includes immunizing a subject with a compositionincluding the antigen. In some embodiments, the subject is a mammal. Insome embodiments, a mammalian subject may include a human, a mouse, adog, a rabbit, a rat, a non-human primate, a sheep, a cat, a horse, acow, a chicken, etc. In some embodiments, the non-human mammal may behumanized; for example, a non-human mammal may include a humanizedmouse. In some embodiments, the subject is a non-mammal including, forexample, an amphibian or a reptile. Immunization may be performed usingany suitable method or combination or methods known to one of skill inthe art.

In some embodiments, immunization may include exposing the subject to atleast one antigen one time, two times, three times, four times, or morethan four times.

In some embodiments, immunization may include exposing the subject tomultiple antigens. For example, in some embodiments, immunization mayinclude exposing the subject to one antigen and boosting with a secondantigen. Such an immunization scheme may be used to develop across-reactive target.

In some embodiments, immunization may preferably include exposing thesubject to a monomeric form of the antigen. In some embodiments,immunization may include exposing the subject to a multimeric form ofthe antigen.

In some embodiments, a composition including the antigen may alsoinclude an adjuvant. In some embodiments, an adjuvant may includeMonophosphoryl Lipid A (MPLA) complete Freund's adjuvant (CFA),incomplete Freund's adjuvant (IFA), alum, etc. In some embodiments,including, for example, when the adjuvant is MPLA, a compositionincluding the antigen and adjuvant may preferably be introduced usingdose escalation. (See for example, Tam et al., Proc Natl Acad Sci USA113(43), E6639-E6648 (2016)). Additionally or alternatively, acomposition may include whole cells which, in the absence of adjuvant,have been found to be highly immunogenic.

In some embodiments, the composition may also include, for example,buffering agents to help to maintain the pH in an acceptable range orpreservatives to retard microbial growth. A composition may alsoinclude, for example, carriers, excipients, stabilizers, chelators,salts, or antimicrobial agents. Acceptable carriers, excipients,stabilizers, chelators, salts, preservatives, buffering agents, orantimicrobial agents, include, but are not limited to, buffers such asphosphate, citrate, and other organic acids; antioxidants includingascorbic acid and methionine; preservatives, such as sodium azide,octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride;benzalkonium chloride, benzethonium chloride; phenol, butyl or benzylalcohol; alkyl parabens such as methyl or propyl paraben; catechol;resorcinol; cyclohexanol; 3-pentanol; and m-cresol; polypeptides;proteins, such as serum albumin, gelatin, or non-specificimmunoglobulins; hydrophilic polymers such as olyvinylpyrrolidone; aminoacids such as glycine, glutamine, asparagine, histidine, arginine, orlysine; monosaccharides, disaccharides, and other carbohydratesincluding glucose, mannose, or dextrins; chelating agents such as EDTA;sugars such as sucrose, mannitol, trehalose or sorbitol; salt-formingcounter-ions such as sodium; metal complexes (for example, Zinc(Zn)-protein complexes); and/or non-ionic surfactants such as TWEEN,PLURONICS, or polyethylene glycol (PEG).

In some embodiments, immunization may preferably include immunizationwith a peptide-MHC complex (p:MHC). The MHC complex may include an MHCClass I complex (MHCI) or an MHC Class II complex (MHCII). Immunizationwith p:MHC may induce a B cell response specific for that peptide in thecontext of MHC. For example, immunization with p:MHCII may induce a Bcell response specific for that peptide in the context of MHCII.

In some embodiments, immunization may include immunizing with an antigenthat comprises at least two peptide-MHC complexes. In some embodiments,the peptide-MHC complexes may include the same MHC, but the peptide ofeach peptide-MHC complex may be different. In some embodiments, the atleast two peptide-MHC complexes may be introduced at different times.

In some embodiments, including for example, when the antigen is used toimmunize a subject, the antigen may preferably be in a monomeric form.In some embodiments, when the antigen is used to immunize a subject, theantigen may be in a multimeric form.

In some embodiments, including for example, when the antigen is used tofor select a subpopulation of cells capable of binding the antigen, theantigen may be in a monomeric or a multimeric form. In some embodiments,when the antigen is used to select for a subpopulation of cells capableof binding the antigen, the antigen is preferably in a multimeric form.A multimeric form of the antigen may include, for example, a dimericantigen, a trimeric antigen, a tetrameric antigen, an octomeric antigen,a dodecamer antigen, or a higher order multimer of antigens.

For example, in some embodiments, the antigen may be linked to (e.g.,conjugated to) a biotin, a desthiobiotin, and/or a fluorescent biotinderivative. Avidin and other biotin-binding proteins, includingstreptavidin and NeutrAvidin Protein, have the ability to bind up tofour biotin molecules, allowing for the formation of a multimericantigen. In some embodiments, a p:MHC may be linked to biotin, and anavidin-biotin interaction may be used to form a p:MHC multimerincluding, for example, a tetramer. In some embodiments the MHC complexof a p:MHC may be linked to biotin.

In some embodiments, a p:MHC may be linked to a histidine tag including,for example, 6× His. In some embodiments the MHC complex of a p:MHC maybe linked to a histidine tag.

In some embodiments, the use of a multimeric antigen may allow for theenrichment of B cells reactive to the antigen by enabling the captureand enrichment of antigen-specific B cells. For example, in someembodiments, a subject may be immunized with a composition comprising anantigen, wherein the antigen comprises a monomeric peptide-MHC complex(p:MHC); a population of cells may be isolated from the subject; and asubpopulation of cells may be enriched from the population of cells byexcluding cells that do not bind to a multimeric form of the antigen.

In some embodiments, a multimeric antigen may be further linked to amarker and/or a photosynthetic pigment including, for example,Phycoerythrin (PE), Allophycocyanin (APC), a BRILLIANT Violetfluorochrome, an Alexa Fluor dye, Fluorescein isothiocyanate (FITC),nanocrystals, synthetic derivatives of fluorescent dyes or molecules,etc.

In some embodiments, the methods described herein further includeisolating a population of cells from the subject after immunization. Thepopulation of cells may include mononuclear cells. In some embodiments,the population of cells preferably includes a B cell. The population ofcells may be isolated from, for example, the subject's blood, spleen,and/or lymph nodes. In some embodiments, the method may include making asingle cell suspension that includes peripheral blood mononuclear cells(PBMCs), splenocytes, and/or a lymphocyte population.

In some embodiments, a method of making a monoclonal antibody asdescribed herein includes enriching (e.g., selecting) a subpopulation ofcells from the population of cells isolated from an immunized subject.In some embodiments, enriching the subpopulation of cells occurs priorto hybridoma formation. In some embodiments, enriching the subpopulationof cells includes increasing the proportion of a subpopulation of cellsby at least 1%, at least 5%, at least 10%, at least 20% at least 30%, atleast 40%, at least 50%, at least 60%, at least 70%, at least 80%, or atleast 90%. In some embodiments, enriching the subpopulation of cellscomprises increasing the proportion of B cells in the population thatbind an antigen including, for example, the antigen (or antigens) usedfor immunization. In some embodiments, enrichment may providesignificant time and cost saving because, for example, fewer coloniesare required for screening and/or a higher percentage of selectedhybridomas produce MAb against the antigen of choice (e.g., a p:MHCII).

In some embodiments, enriching the subpopulation of cells includesexcluding cells that do not bind to the antigen. For example, if theantigen includes a peptide-MHC complex (p:MHC), enriching thesubpopulation of cells includes excluding cells that do not bind top:MHC. Alternatively or additionally, if the antigen includes apeptide-MHC complex (p:MHC), enriching the subpopulation of cells caninclude excluding cells that bind to the MHC complex not bound to thepeptide or to the peptide not bound to the MHC complex. In someembodiments, excluding cells that bind to the MHC complex not bound tothe peptide may include identifying cells that bind to an antigen thatincludes the same MHC and a different peptide. In some embodiments,excluding cells that bind to the peptide not bound to the MHC complexmay include identifying cells that bind to the peptide bound to adifferent MHC complex and/or to unbound peptide. In some embodiments,excluding cells that do not bind to the antigen may include identifyingcells that bind to a structural component of the antigen (e.g., alinker, a marker, etc.) other than the MHC and the peptide.

In embodiments where a composition including the antigen also includesan adjuvant, excluding cells that do not bind to the antigen may includeexcluding cells that bind to the adjuvant.

In some embodiments, enriching the subpopulation of cells includesenriching a subpopulation of cells capable of binding to a multimericform of the antigen. A multimeric antigen may be used, for example, toconfirm the expansion of a population of antigen-specific-B cells.

In some embodiments, enriching a subpopulation of cells includesincreasing the proportion of B cells in the population that bind theantigen. In other words, the population of cells may include B cellsspecific for the antigen of interest (that is, an antigen-specific Bcell), and these cells may be selected for. Enriching B cells specificfor the antigen of interest prior to myeloma fusion may significantlyreduce the screening required after fusion.

In some embodiments, enrichment of the subpopulation of cells mayinclude magnetic enrichment for a B cell that binds to a multimericantigen. In some embodiments, magnetic enrichment may include the use ofa magnetic bead. In some embodiments, the magnetic bead may bind to amarker and/or a photosynthetic pigment. In some embodiments, amultimeric antigen may preferably include a p:MHC multimer.

In some embodiments, a multimeric antigen may include a marker and/or aphotosynthetic pigment. In some embodiments, a B cell bound to amultimeric antigen may be enriched for using a reagent specific to themarker and/or a photosynthetic pigment including, for example, amagnetic bead. The marker and/or photosynthetic pigment may include, forexample, Phycoerythrin (PE), Allophycocyanin (APC), a BRILLIANT Violetfluorochrome, an Alexa Fluor dye, Fluorescein isothiocyanate (FITC),nanocrystals, synthetic derivatives of fluorescent dyes or molecules,etc. For example, when a multimeric antigen includes PE, a B cell boundto the PE-multimeric antigen may be selected by using an anti-PEmagnetic bead; when a multimeric antigen includes APC, a B cell bound tothe APC-multimeric antigen may be selected by using an anti-APC magneticbead.

In some embodiments, as described in an exemplary embodiment in Example2, a multimeric antigen may include a p:MHC tetramer PE including, forexample, p63:IA^(g7) tetramer:PE.

In some embodiments, enrichment the subpopulation of cells may includeusing a non-specific antigen, that is, a different antigen than theantigen used to immunize the subject (e.g., a decoy antigen). In someembodiments, the non-specific antigen may be multimeric. For example, anon-specific antigen may be used determine if a B cell binds to anon-specific antigen.

For example, when the subject has been immunized with a peptide-MHCcomplex (p:MHC), the cells may be screened for binding to a secondp:MHC, where the second p:MHC includes a different MHC complex or adifferent antigen, and cells that bind to the second p:MHC may beexcluded. In some embodiments, the second p:MHC may preferably bemultimeric. In some embodiments, the second p:MHC preferably includesthe same MHC complex as the p:MHC of the antigen used to immunize thesubject but a different peptide than the p:MHC of the antigen used toimmunize the subject.

In some embodiments, enriching the subpopulation of cells using amultimeric antigen may reduce the number of cells compared to thestarting population by at least 2-fold, at least 5-fold, at least10-fold, at least 15-fold, at least 20-fold, or at least 23-fold.

In some embodiments, enriching the subpopulation of cells may includeflow cytometric identification of cells. In some embodiments,identification of cells includes identification of mononuclear cells. Insome embodiments, enriching the subpopulation of cells may furtherinclude sorting. For example, mononuclear cells may be identified and/orsorted by identifying expression of a lymphocyte marker (e.g., CD45)including, for example, identifying expression of a B cell marker (e.g.,CD220); identifying a plasma cell marker (e.g., CD138); by testing forviability (e.g., using a GHOST DYE including, for example, GHOST DYEViolet 510; propidium iodide; 7 Amino-Actinomycin D (7AAD), etc.);and/or by testing for antigen specificity. In some embodiments,enriching the subpopulation of cells may include flow cytometricidentification of undesired cell types. Enriching the subpopulation ofcells may further include excluding the undesired cell types (e.g., byflow cytometric sorting). For example, in some embodiments, it may bedesirable to exclude T cells (e.g., cells expressing CD90), macrophages(e.g., cells expressing F4/80), dendritic cells (e.g., cells expressingCD11c), and/or granulocytes (e.g., cells expressing GR-1) from asubpopulation of cells. In some embodiments, testing for antigenspecificity may include determining if a cell is capable of binding toan antigen. In some embodiments, an antigen may include a p:MHC. In someembodiments, an antigen may include a multimeric antigen.

In some embodiments, enriching the subpopulation of cells using sortingmay reduce the number of cells compared to the starting population by atleast 5-fold, at least 10-fold, at least 20-fold, at least 30-fold, atleast 40-fold, at least 50-fold, at least 100-fold, at least 200-fold,or at least 500-fold.

In some embodiments, enriching the subpopulation of cells using sortingmay provide a population of cells that is at least 80%, at least 85%, atleast 90%, at least 95%, at least 96%, at least 97%, at least 98%, or atleast 99% cells identified by a marker or combination of markers. Forexample, the marker or combination of markers may be used to identify aB cell and/or a plasma cell.

In some embodiments, the methods described herein may be used togenerate additional p:MHCII targeted MAbs. At the time of the invention,few p:MHCII targeted MAbs existed. The most well-known p:MHCII targetedMAb is the Y-Ae antibody (anti-Eα:IA^(b)), which recognizes Eα₅₂₋₆₈bound to IA^(b) MHCII molecules and was used to understand centraltolerance and alloreactive antigen presentation. The efficiency of Y-Aegeneration has not been described in the literature, however, thegeneration of MAbs specific for two different peptides of hen egglysozyme (HEL) provides insight into the inefficiency of the process.Specifically, two HEL_(46_61):IA^(k) (clones B6G and C4H) MAb wereidentified by screening 500 clones (Zhong et al. Proc Natl Acad Sci USA94, 13856-13861 (1997)). An additional clone specifically recognizingHEL₁₁₆₋₁₂₉:IA^(k) (D8H) was identified by screening 500 differentcolonies. However, these clones were found to also weakly stain cellsexpressing IA^(k) in an HEL-independent manner (Zhong et al. Proc NatlAcad Sci USA 94, 13856-13861 (1997)). In a separate report, a clonespecific for HEL₄₈₋₆₂:IA^(k) (Aw3.18) was generated by screening 1000colonies (Dadaglio et al. Immunity 6, 727-738 (1997)). Thus, theefficiency of generating a MAb clone using conventional approaches hasbeen reported to range from 1:250 to 1:1000 or (0.1 to 0.4%). Incontrast, the methods described herein, as exemplified by Table 1,describe a range of 1:18 to 1:115 (0.9 to 13.5%). That is, the successrate of the methods described herein may be at least 2.25 to 33.75 foldhigher than traditional approaches. Moreover, because fewer clones arerequired for positive identification, fewer hours and resources arerequired for hybridoma screening.

In some embodiments, a method of making a monoclonal antibody asdescribed herein includes forming a hybridoma. In some embodiments,forming a hybridoma includes forming a hybridoma from a cell selectedfrom the subpopulation of cells enriched as described herein. In someembodiments, the cell selected from the subpopulation of cells enrichedas described herein is preferably a B cell. A hybridoma may be obtainedby methods known to those skilled in the art. In some embodiments, thecell selected from the subpopulation of cells enriched as describedherein is fused with another cell. In some embodiments, forming ahybridoma may include hypoxanthine-aminopterin-thymidine (HAT)selection.

In some embodiments, a method of making a monoclonal antibody asdescribed herein includes screening a hybridoma for production of anantibody specific to an antigen of interest including, for example, andan antibody that binds the antigen used for immunization. In someembodiments, screening a hybridoma may include determining if itproduces an antibody that binds a non-specific antigen and/or a decoyantigen. In some embodiments, when the antigen includes a p:MHC, a decoyantigen may include a different peptide bound to the same MHC complex asthe p:MHC. A hybridoma may be screened by methods known to those skilledin the art.

Surprisingly, in contrast to traditional methods that typically yieldfewer than 1% hybridomas specific for a protein target antigen, themethods described herein produce a much higher yield of hybridomasspecific for a protein target. The methods provide herein areunexpectedly efficient at generating a monoclonal antibody thatrecognizes a peptide-MHC complex.

In some embodiments, a hybridoma may include, for example, the followinghybridomas of Example 2: A1, A3, A5, B3, C5, C6, C8, F2, F7, and/or G8.In some embodiments, the hybridoma may preferably express an antibodythat recognizes p63:IA^(g7). In some embodiments, the hybridoma maypreferably express an antibody that recognizes 2W:IA^(b). In someembodiments, a hybridoma may include, for example, Ins 4G8 (alsoreferred to herein as 4G8). In some embodiments, the hybridoma maypreferably express an antibody that recognizes p8E: IA^(g7) and/orp8G:IA^(g7).

This disclosure also describes monoclonal antibodies that recognizepeptide:MHCII (p:MHCII) (also referred to herein as an anti-p:MHCIIMAb).

An intact antibody molecule has two heavy (H) chain variable regions(abbreviated herein as V_(H)) and two light (L) chain variable regions(abbreviated herein as V_(L)). The V_(H) and V_(L) regions may befurther subdivided into regions of hypervariability, termed“complementarity determining regions” (“CDRs”), interspersed withregions that are more conserved, termed “framework regions” (“FRs”). Theextent of the FRs and CDRs has been precisely defined (see, Kabat, E.A., et al. (1991) Sequences of Proteins of Immunological Interest, FifthEdition, U.S. Department of Health and Human Services, NIH PublicationNo. 91-3242, and Chothia, C. et al., J. Mol. Biol. 1987; 196: 901-917).Each V_(H) and V_(L) is composed of three CDRs and four FRs, arrangedfrom amino-terminus to carboxy-terminus in the following order: FR1,CDR1, FR2, CDR2, FR3, CDR3, FR4.

In some embodiments, an anti-p:MHCII MAb may include, for example,antibody FS1. In some embodiments, FS1 may be produced by hybridoma A1.In some embodiments, a monoclonal antibody includes a monoclonalantibody having the same heavy chain as FS1. In some embodiments, amonoclonal antibody includes a monoclonal antibody having the same lightchain as FS1. In some embodiments, a monoclonal antibody may containone, two, three, four, five, six, or more amino acid substitutions inthe heavy and/or the light chains of FS1 wherein the amino acidsubstitutions do not substantially affect binding of the antibody top63:IA^(g7). In some embodiments, a monoclonal antibody includes amonoclonal antibody having the same V_(H) domain as FS1. In someembodiments, a monoclonal antibody includes a monoclonal antibody havingthe same V_(L) domain as FS1. In some embodiments, a monoclonal antibodyincludes a monoclonal antibody having the same V_(H) domain and the sameV_(L) domain as FS1. In some embodiments, a monoclonal antibody cancontain one, two, three, four, five, six, or more amino acidsubstitutions in the V_(H) domains and/or the V_(L) domains identifiedabove which do not substantially affect binding of the antibody top63:IA^(g7). In some embodiments, a monoclonal antibody includes amonoclonal antibody having at least one CDR region of the V_(H) domainof FS1, at least two CDR regions of the V_(H) domain of FS1, or at leastthree CDR regions of the V_(H) domain of FS1. Additionally oralternatively, in some embodiments, a monoclonal antibody includes amonoclonal antibody having at least one CDR region of the V_(L) domainof FS1, at least two CDR regions of the V_(L) domain of FS1, or at leastthree CDR regions of the V_(L) domain of FS1. In some embodiments, amonoclonal antibody may contain one, two, three, four, five, six, ormore amino acid substitutions in one or more CDR regions identifiedabove which do not substantially affect binding of the antibody top63:IA^(g7).

In some embodiments, an anti-p:MHCII MAb may include, for example,antibody W6. In some embodiments, W6 may be produced by hybridoma A1. Insome embodiments, a monoclonal antibody includes a monoclonal antibodyhaving the same heavy chain as W6. In some embodiments, a monoclonalantibody includes a monoclonal antibody having the same light chain asW6. In some embodiments, a monoclonal antibody may contain one, two,three, four, five, six, or more amino acid substitutions in the heavyand/or the light chains of W6 wherein the amino acid substitutions donot substantially affect binding of the antibody to 2W:IA^(b). In someembodiments, a monoclonal antibody includes a monoclonal antibody havingthe same V_(H) domain as W6. In some embodiments, a monoclonal antibodyincludes a monoclonal antibody having the same V_(L) domain as W6. Insome embodiments, a monoclonal antibody includes a monoclonal antibodyhaving the same V_(H) domain and the same V_(L) domain as W6. In someembodiments, a monoclonal antibody can contain one, two, three, four,five, six, or more amino acid substitutions in the V_(H) domains and/orthe V_(L) domains identified above which do not substantially affectbinding of the antibody to 2W:IA^(b). In some embodiments, a monoclonalantibody includes a monoclonal antibody having at least one CDR regionof the V_(H) domain of W6, at least two CDR regions of the V_(H) domainof W6, or at least three CDR regions of the V_(H) domain of W6.Additionally or alternatively, in some embodiments, a monoclonalantibody includes a monoclonal antibody having at least one CDR regionof the V_(L) domain of W6, at least two CDR regions of the V_(L) domainof W6, or at least three CDR regions of the V_(L) domain of W6. In someembodiments, a monoclonal antibody may contain one, two, three, four,five, six, or more amino acid substitutions in one or more CDR regionsidentified above which do not substantially affect binding of theantibody to 2W:IA^(b).

In some embodiments, an anti-p:MHCII MAb may include, for example,antibody XRI1. In some embodiments, XRI1 may be produced by hybridomaIns 4G8 (also referred to herein as 4G8). In some embodiments, amonoclonal antibody includes a monoclonal antibody having the same heavychain as XRI1. In some embodiments, a monoclonal antibody includes amonoclonal antibody having the same light chain as XRI1. In someembodiments, a monoclonal antibody may contain one, two, three, four,five, six, or more amino acid substitutions in the heavy and/or thelight chains of XRI1 wherein the amino acid substitutions do notsubstantially affect binding of the antibody to p8E:IA^(g7) and/orp8G:IA^(g7). In some embodiments, a monoclonal antibody includes amonoclonal antibody having the same V_(H) domain as XRI1. In someembodiments, a monoclonal antibody includes a monoclonal antibody havingthe same V_(L) domain as XRI1. In some embodiments, a monoclonalantibody includes a monoclonal antibody having the same V_(H) domain andthe same V_(L) domain as XRI1. In some embodiments, a monoclonalantibody can contain one, two, three, four, five, six, or more aminoacid substitutions in the V_(H) domains and/or the V_(L) domainsidentified above which do not substantially affect binding of theantibody to p8E:IA^(g7) and/or p8G:IA^(g7). In some embodiments, amonoclonal antibody includes a monoclonal antibody having at least oneCDR region of the V_(H) domain of XRI1, at least two CDR regions of theV_(H) domain of XRI1, or at least three CDR regions of the V_(H) domainof XRI1. Additionally or alternatively, in some embodiments, amonoclonal antibody includes a monoclonal antibody having at least oneCDR region of the V_(L) domain of XRI1, at least two CDR regions of theV_(L) domain of XRI1, or at least three CDR regions of the V_(L) domainof XRI1. In some embodiments, a monoclonal antibody may contain one,two, three, four, five, six, or more amino acid substitutions in one ormore CDR regions identified above which do not substantially affectbinding of the antibody to p8E:IA^(g7) and/or p8G:IA^(g7).

In some embodiments, a monoclonal antibody can contain one, two, three,four, five, six, or more amino acid substitutions in one or moreframework regions (FRs). In some embodiments, the substitutions orsubstitutions in the framework regions (FRs) do not substantially affectbinding of the antibody to PE.

This disclosure also describes monoclonal antibodies that recognizephycoerythrin (PE).

In some embodiments, an antibody that recognizes PE is produced by aclone described in Example 3 and FIG. 14 . In some embodiments, anantibody that recognizes PE includes an antibody of FIG. 23 . In someembodiments, an antibody that recognizes PE includes a monoclonalantibody having the same heavy chain as a heavy chain of FIG. 23 . Insome embodiments, an antibody that recognizes PE includes a monoclonalantibody having the same light chain as a light chain of FIG. 23 . Insome embodiments, a monoclonal antibody may contain one, two, three,four, five, six, or more amino acid substitutions in the heavy and/orthe light chains of an antibody of FIG. 23 wherein the amino acidsubstitutions do not substantially affect binding of the antibody to PE.In some embodiments, a monoclonal antibody includes a monoclonalantibody having the same V_(H) domain as a V_(H) domain of FIG. 23 . Insome embodiments, a monoclonal antibody includes a monoclonal antibodyhaving the same V_(L) domain as a V_(L) domain of FIG. 23 . In someembodiments, a monoclonal antibody includes a monoclonal antibody havingthe same V_(H) domain and V_(L) domain as a V_(H) domain and V_(L)domain of FIG. 23 . In some embodiments, a monoclonal antibody cancontain one, two, three, four, five, six, or more amino acidsubstitutions in the V_(H) domains and/or the V_(L) domains identifiedabove which do not substantially affect binding of the antibody to PE.

In some embodiments, an antibody that recognizes PE includes amonoclonal antibody having at least one CDR, at least two CDRs, or atleast three CDRs of a V_(H) domain of FIG. 23 . In some embodiments, anantibody that recognizes PE includes a monoclonal antibody having atleast one CDR, at least two CDRs, or at least three CDRs of a V_(L)domain of FIG. 23 . In some embodiments, a monoclonal antibody cancontain one, two, three, four, five, six, or more amino acidsubstitutions in one or more CDRs identified above which do notsubstantially affect binding of the antibody to PE.

In some embodiments, any of the monoclonal antibodies described hereincan contain one, two, three, four, five, six, or more amino acidsubstitutions in one or more framework regions (FRs). In someembodiments, the substitutions or substitutions in the framework regions(FRs) do not substantially affect binding of the antibody to thecorresponding antigen.

In another aspect, this disclosure describes an isolated polynucleotidemolecule. In some embodiments, the isolated polynucleotide moleculeincludes a nucleotide sequence encoding a monoclonal antibody. In someembodiments, the isolated polynucleotide molecule includes a nucleotidesequence that has at least 75%, at least 80%, at least 85%, at least90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least99% sequence identity to a nucleotide sequence encoding a monoclonalantibody described herein or a portion of a monoclonal antibodydescribed herein.

The antibody may be an antibody from any suitable species. In someembodiments, the antibody may be a mouse antibody. In some embodiments,the antibody may be a rat antibody. In some embodiments, the antibodymay be a rabbit antibody.

In some embodiments, the antibodies described herein (includingantibodies produced by the methods described herein) may be humanized.An antibody can be humanized by any suitable method. Techniques forproducing humanized monoclonal antibodies can be found, for example, inJones et al., Nature (1986) 321:522 and Singer et al., J. Immunol.,(1993) 150:2844. For example, humanization of the antibody can includechanges to the antibody to reduce the immunogenicity of the antibodywhen used in humans. In some embodiments, a humanized antibody caninclude at least a portion of an immunoglobulin constant region (Fc) ofa human immunoglobulin. A humanized antibody can include, in someembodiments, a human immunoglobulin (recipient antibody) in whichresidues from one or more complementary determining regions (CDRs) ofthe recipient antibody are replaced by residues from one or more CDRs ofa non-human species antibody (donor antibody), such as mouse, rat, orrabbit antibody. In some embodiments, Fv framework residues of a humanimmunoglobulin can be replaced by corresponding non-human residues.

In some embodiments, the antibody is an IgG antibody. In someembodiments, the antibody may be an antibody or an IgG subclassincluding, for example, IgG1, IgG2, IgG3 or IgG4. In some embodiments,the antibody may be a mouse IgG of one of the following sub-classes:IgG1, IgG2A, IgG2B, IgG2C and IgG3. In some embodiments, the antibodymay be a rat IgG of one of the following sub-classes: IgG1, IgG2A,IgG2B, or IgG2C.

In some embodiments, the antibody may include a kappa light chain. Insome embodiments, the antibody may include a lambda light chain.

In some embodiments, the monoclonal antibody includes an antigen-bindingfragment including an Fab fragment, an Fab′ fragment, an F(ab)₂fragment, and/or an Fv fragment.

The antibodies described herein (including antibodies produced by themethods described herein) and compositions including the antibodiesdescribed herein may be used for any suitable use.

For example, in some embodiments, the antibodies may be used to blockantigen presentation to T or B cells during bacterial or viralpathogenesis and/or to provide mechanistic insight for immunity andregulation.

In some embodiments, the antibodies including, for example, an MAbspecific for p:MHC, may be used to study specific subsets of antigenpresenting cells during immune recognition (e.g., from immunehomeostasis to defining novel roles for multiple subsets of antigenpresenting cells responding to vaccination and infection).

In some embodiments, the antibodies can be used to treat a disorderincluding, for example, an autoimmune-related disorder. In someembodiments, the disorder could include diabetes. For example, in someembodiments, the antibodies described herein including, for example,XRI1, a humanized version of XRI1, or an antibody including a componentof XRI1 (e.g., a heavy chain, a light chain, a V_(H) domain, a V_(L)domain and/or a CDR of XRI1) could be used in an antigen-specifictherapeutic approach to treat diabetes.

In some embodiments, this disclosure describes a composition includingat least one of the antibodies describes herein.

In some embodiments, the composition may also include, for example,buffering agents to help to maintain the pH in an acceptable range orpreservatives to retard microbial growth. A composition may alsoinclude, for example, carriers, excipients, stabilizers, chelators,salts, or antimicrobial agents. Acceptable carriers, excipients,stabilizers, chelators, salts, preservatives, buffering agents, orantimicrobial agents, include, but are not limited to, buffers such asphosphate, citrate, and other organic acids; antioxidants includingascorbic acid and methionine; preservatives, such as sodium azide,octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride;benzalkonium chloride, benzethonium chloride; phenol, butyl or benzylalcohol; alkyl parabens such as methyl or propyl paraben; catechol;resorcinol; cyclohexanol; 3-pentanol; and m-cresol; polypeptides;proteins, such as serum albumin, gelatin, or non-specificimmunoglobulins; hydrophilic polymers such as olyvinylpyrrolidone; aminoacids such as glycine, glutamine, asparagine, histidine, arginine, orlysine; monosaccharides, disaccharides, and other carbohydratesincluding glucose, mannose, or dextrins; chelating agents such as EDTA;sugars such as sucrose, mannitol, trehalose or sorbitol; salt-formingcounter-ions such as sodium; metal complexes (for example, Zinc(Zn)-protein complexes); and/or non-ionic surfactants such as TWEEN,PLURONICS, or polyethylene glycol (PEG).

In some embodiments, the composition is a pharmaceutical composition andincludes the monoclonal antibody and a pharmaceutically acceptablecarrier, diluent or excipient. In the preparation of the pharmaceuticalcompositions comprising the antibodies described in the teachingsherein, a variety of vehicles and excipients may be used, as will beapparent to the skilled artisan.

The pharmaceutical compositions will generally comprise apharmaceutically acceptable carrier and a pharmacologically effectiveamount of an antibody, or mixture of antibodies.

The pharmaceutical composition may be formulated as a powder, a granule,a solution, a suspension, an aerosol, a solid, a pill, a tablet, acapsule, a gel, a topical cream, a suppository, a transdermal patch,and/or another formulation known in the art.

For the purposes described herein, pharmaceutically acceptable salts ofan antibody are intended to include any art-recognized pharmaceuticallyacceptable salts including organic and inorganic acids and/or bases.Examples of salts include but are not limited to sodium, potassium,lithium, ammonium, calcium, as well as primary, secondary, and tertiaryamines, esters of lower hydrocarbons, such as methyl, ethyl, and propyl.Other salts include but are not limited to organic acids, such as aceticacid, propionic acid, pyruvic acid, maleic acid, succinic acid, tartaricacid, citric acid, benzoic acid, cinnamic acid, salicylic acid, etc.

As used herein, “pharmaceutically acceptable carrier” comprises anystandard pharmaceutically accepted carriers known to those of ordinaryskill in the art in formulating pharmaceutical compositions. Forexample, the antibody may be prepared as a formulation in apharmaceutically acceptable diluent, including for example, saline,phosphate buffer saline (PBS), aqueous ethanol, or solutions of glucose,mannitol, dextran, propylene glycol, oils (e.g., vegetable oils, animaloils, synthetic oils, etc.), microcrystalline cellulose, carboxymethylcellulose, hydroxylpropyl methyl cellulose, magnesium stearate, calciumphosphate, gelatin, polysorbate 80 or as a solid formulation in anappropriate excipient.

A pharmaceutical composition will often further comprise one or morebuffers (e.g., neutral buffered saline or phosphate buffered saline),carbohydrates (e.g., glucose, sucrose or dextrans), mannitol, proteins,polypeptides or amino acids such as glycine, antioxidants (e.g.,ascorbic acid, sodium metabisulfite, butylated hydroxytoluene, butylatedhydroxyanisole, etc.), bacteriostats, chelating agents such as EDTA orglutathione, adjuvants (e.g., aluminium hydroxide), solutes that renderthe formulation isotonic, hypotonic or weakly hypertonic with the bloodof a recipient, suspending agents, thickening agents and/orpreservatives. Alternatively, compositions of the present invention maybe formulated as a lyophilizate.

Any suitable carrier known to those of ordinary skill in the art may beemployed in a composition including at least one of the antibodiesdescribes herein. Antibody compositions may be formulated for anyappropriate manner of administration, including for example, oral,nasal, mucosal, intravenous, intraperitoneal, intradermal, subcutaneous,and intramuscular administration.

A compositions of the present disclosure may be formulated in apharmaceutical preparation in a variety of forms adapted to the chosenroute of administration. One of skill will understand that thecomposition will vary depending on mode of administration and dosageunit. For example, for parenteral administration, isotonic saline can beused. For topical administration a cream, including a carrier such asdimethylsulfoxide (DMSO), or other agents typically found in topicalcreams that do not block or inhibit activity of the peptide, can beused. Other suitable carriers include, but are not limited to alcohol,phosphate buffered saline, and other balanced salt solutions. Thecompounds of this invention can be administered in a variety of ways,including, but not limited to, intravenous, topical, oral, subcutaneous,intraperitoneal, and intramuscular delivery. In some aspects, thecompounds of the present invention may be formulated for controlled orsustained release. In some aspects, a formulation for controlled orsustained release is suitable for subcutaneous implantation. In someaspects, a formulation for controlled or sustained release includes apatch. A compound may be formulated for enteral administration, forexample, formulated as a capsule or tablet.

Administration may be as a single dose or in multiple doses. In someembodiments, the dose is an effective amount as determined by thestandard methods, including, but not limited to, those described herein.Those skilled in the art of clinical trials will be able to optimizedosages of particular compounds through standard studies. Additionally,proper dosages of the compositions can be determined without undueexperimentation using standard dose-response protocols. Administrationincludes, but is not limited to, any of the dosages and dosingschedules, dosing intervals, and/or dosing patterns described in theexamples included herewith.

The composition including an antibody according to the presentdisclosure can be administered by any suitable means including, but notlimited to, for example, oral, rectal, nasal, topical (includingtransdermal, aerosol, buccal and/or sublingual), vaginal, parenteral(including subcutaneous, intramuscular, and/or intravenous),intradermal, intravesical, intra-joint, intra-arteriole,intraventricular, intracranial, intraperitoneal, intranasal, byinhalation, or intralesional (for example, by injection into or around atumor).

For parenteral administration in an aqueous solution, for example, thesolution should be suitably buffered if necessary and the liquid diluentfirst rendered isotonic with sufficient saline or glucose. Theseparticular aqueous solutions are especially suitable for intravenous,intramuscular, subcutaneous, and intraperitoneal administration. In thisconnection, sterile aqueous media that can be employed will be known tothose of skill in the art. Some variation in dosage will necessarilyoccur depending on the condition of the subject being treated. Theperson responsible for administration will, in any event, determine theappropriate dose for the individual subject. Moreover, for humanadministration, preparations should meet sterility, pyrogenicity, andgeneral safety and purity standards as required by the FDA. Suchpreparation may be pyrogen-free.

Many suitable formulations are known, including polymeric or proteinmicroparticles encapsulating drug to be released, ointments, gels, orsolutions which can be used topically or locally to administer drug, andeven patches, which provide controlled release over a prolonged periodof time. These can also take the form of implants. Such an implant maybe implanted within the tumor.

The compounds of the present invention can also be provided in alyophilized form. Such compositions may include a buffer, e.g.,bicarbonate, for reconstitution prior to administration, or the buffermay be included in the lyophilized composition for reconstitution with,e.g., water. The lyophilized composition may further comprise a suitablevasoconstrictor, e.g., epinephrine. The lyophilized composition can beprovided in a syringe, optionally packaged in combination with thebuffer for reconstitution, such that the reconstituted composition canbe immediately administered to a patient.

As used herein “treating” or “treatment” can include therapeutic and/orprophylactic treatments. “Treating a disorder,” as used herein, is notintended to be an absolute term. Treatment may lead to an improvedprognosis or a reduction in the frequency or severity of symptoms. A“therapeutically effective” concentration or amount as used herein is anamount that provides some improvement or benefit to the subject.Desirable effects of treatment include preventing occurrence orrecurrence of disease, alleviation of symptoms, diminishment of anydirect or indirect pathological consequences of the disease, decreasingthe rate of disease progression, amelioration or palliation of thedisease state, and remission or improved prognosis. Likewise, the term“preventing,” as used herein, is not intended as an absolute term.Instead, prevention refers to delay of onset, reduced frequency ofsymptoms, or reduced severity of symptoms associated with a disorder.Prevention therefore refers to a broad range of prophylactic measuresthat will be understood by those in the art. In some circumstances, thefrequency and severity of symptoms is reduced to non-pathologicallevels. In some circumstances, the symptoms of an individual receivingthe compositions of the invention are only 90%, 80%, 70%, 60%, 50%, 40%,30%, 20%, 10%, 5%, or 1% as frequent or severe as symptoms experiencedby an untreated individual with the disorder.

Therapeutically effective concentrations and amounts may be determinedfor each application herein empirically by testing the compounds inknown in vitro and in vivo systems, such as those described herein,dosages for humans or other animals may then be extrapolated therefrom.

It is understood that the precise dosage and duration of treatment is afunction of the disease being treated and may be determined empiricallyusing known testing protocols or by extrapolation from in vivo or invitro test data. It is to be noted that concentrations and dosage valuesmay also vary with the severity of the condition to be alleviated. It isto be further understood that for any particular subject, specificdosage regimens should be adjusted over time according to the individualneed and the professional judgment of the person administering orsupervising the administration of the compositions, and that theconcentration ranges set forth herein are exemplary only and are notintended to limit the scope or practice of the claimed compositions andmethods.

Toxicity and therapeutic efficacy of the compositions can be determinedby standard pharmaceutical procedures in cell cultures or experimentalanimals, for example, for determining the LD₅₀ (the dose lethal to 50%of the population) and the ED₅₀ (the dose therapeutically effective in50% of the population). The dose ratio between toxic and therapeuticeffects is the therapeutic index and it can be expressed as the ratiobetween LD₅₀ and ED₅₀. Compositions that exhibit high therapeuticindices can be preferred. The data obtained from cell culture assays andanimal studies can be used in formulating a range of dosage for use inhumans. The dosage of such compositions can preferably lie within arange of circulating concentrations that include the ED₅₀ with little orno toxicity. The dosage can vary within this range depending upon thedosage form employed and the route of administration utilized. The exactformulation, route of administration and dosage can be chosen by theindividual physician in view of the patient's condition.

A composition as described herein may be administered at once, or may bedivided into a number of smaller doses to be administered at intervalsof time. For example, compositions may be administered repeatedly, e.g.,at least 2, 3, 4, 5, 6, 7, 8, or more times, or may be administered bycontinuous infusion. It is understood that the precise dosage andduration of treatment is a function of the disease being treated and maybe determined empirically using known testing protocols or byextrapolation from in vivo or in vitro test data. It is to be noted thatconcentrations and dosage values may also vary with the severity of thecondition to be alleviated. It is to be further understood that for anyparticular subject, specific dosage regimens should be adjusted overtime according to the individual need and the professional judgment ofthe person administering or supervising the administration of thecompositions, and that the concentration ranges set forth herein areexemplary only and are not intended to limit the scope or practice ofthe claimed compositions and methods.

In some therapeutic embodiments, an “effective amount” of an agent is anamount that results in a reduction of at least one pathologicalparameter. Thus, for example, in some aspects of the present disclosure,an effective amount is an amount that is effective to achieve areduction of at least 10%, at least 15%, at least 20%, at least 25%, atleast 30%, at least 35%, at least 40%, at least 45%, at least 50%, atleast 55%, at least 60%, at least 65%, at least 70%, at least 75%, atleast 80%, at least 85%, at least 90%, or at least 95% compared to theexpected reduction in the parameter in an individual not treated withthe agent.

In some aspects of the methods of the present disclosure, a methodfurther includes the administration of one or more additionaltherapeutic agents. One or more additional therapeutic agents may beadministered before, after, and/or coincident to the administration of amonoclonal antibody as described herein. An additional therapeutic agentcan include, for example, chemotherapy, radiation therapy, etc.Additional therapeutic agents may be administered separately or as partof a mixture or cocktail. In some aspects of the present disclosure, theadministration of an antibody may allow for the effectiveness of a lowerdosage of other therapeutic modalities when compared to theadministration of the other therapeutic modalities alone, providingrelief from the toxicity observed with the administration of higherdoses of the other modalities.

In some aspects of the methods of the present disclosure, theadministration a composition as described herein and the at least oneadditional therapeutic agent demonstrate therapeutic synergy. In someaspects of the methods of the present disclosure, a measurement ofresponse to treatment observed after administering both an antibody asdescribed herein and the additional therapeutic agent is improved overthe same measurement of response to treatment observed afteradministering either the antibody or the additional therapeutic agentalone.

As used herein, the term “subject” includes, but is not limited to,humans and non-human vertebrates. In some embodiments, a subject is amammal, particularly a human. A subject may be an individual. A subjectmay be an “individual,” “patient,” or “host.” Non-human vertebratesinclude livestock animals, companion animals, and laboratory animals. Anon-human subject also may include a non-human primate as well as arodent, such as, but not limited to, a rat or a mouse. A non-humansubject also may include, without limitation, a chicken, a horse, a cow,a pig, a goat, a dog, a cat, a guinea pig, a hamster, a mink, a rabbit,etc.

The present invention is illustrated by the following examples. It is tobe understood that the particular examples, materials, amounts, andprocedures are to be interpreted broadly in accordance with the scopeand spirit of the invention as set forth herein.

EXAMPLES Example 1

BDC2.5 CD4⁺ T cells are used in mouse models of Type 1 Diabetes (T1D),as the transfer of activated cells results in rapid diabetespathogenesis. Chromogranin A has been shown to be the natural ligand ofBDC2.5 CD4⁺ T cells as well as an autoantigen in human studies of T1D.However, the exact role of this autoantigen is unknown due to lack ofreagents. Two peptide mimotopes, p31 and p63, share a common amino acidmotif with a natural cleavage product of Chromogranin A, WE14. ThisExample describes the generation of a broadly cross reactive antibodyagainst two BDC2.5 T cell mimotopes by priming and boosting with the twodistinct monomers.

BDC2.5 T cells recognize WE14, a cleavage product of Chromogranin A,which shares a common five amino acid motif with two T cell activatingmimotopes, peptide 31 (p31) and p63 (FIG. 1 ). (Stadinski et al. NatImmunol. 11(3):225-31 (2010); Marrack et al. Cold Spring Hard PerspectMed. 2(9):a007765 (2012).)

Mice were immunized according to the immunization scheme shown in FIG. 2. Antibody-expressing cells were isolated according to the scheme shownin FIG. 3 . 480 hybridomas were generated by fusion ofantibody-expressing cells with parental myeloma cells, and antibodieswere harvested and screened for reactivity with monomers using ELISA. 14clones were found to be reactive to p31:IA^(g7) but not anhCLIP:IA^(g7). 12 of the 14 clones were cross-reactive to p31:IA^(g7)and p63:IA^(g7). A representative cross-reactive ELISA result is shownin FIG. 4 . As shown in FIG. 5 , a high proportion of detectedantibodies were IgM but a diverse array of IgG subtypes were alsoobtained.

Example 2

This Example describes a methodology that may be used to generate amonoclonal antibody (MAb) including, for example, a MAb against aspecific peptide MHCII complex.

Methods

Mice. Female NOD mice (6-8 weeks of age) were purchased from TaconicBiosciences (Hudson, NY). Female C57BL/6 (6-8 weeks of age), female 129(6-8 weeks of age), and female BALB/c mice (8-10 weeks of age) werepurchased from the Jackson Laboratory (Bar Harbor, ME). Female (6 weekold) NOD.BDC2.5 Thy1.1 transgenic mice were bred under specificpathogen-free, barrier facility at the University of Minnesota. Animalswere housed under specific pathogen-free, barrier facility in accordancewith NIH guidelines. All animal procedures were approved by theUniversity of Minnesota or Tulane Institutional Animal Care and UseCommittee.

Peptides. Peptides used for in vivo immunization and in vitrostimulation and peptide pulsing include p63 (RTRPLWVRME) (SEQ ID NO:5),p31 (YVRPLWVRME) (SEQ ID NO:6), OVA₁₄₁₋₁₆₀ (CARELINSWVESQTNGIIRN) (SEQID NO:7) (Genemed Synthesis, San Antonio, TX), 2W (EAWGALANWAVDSA) (SEQID NO:8) (Genscript, Piscataway, NJ).

Peptide:MHCII monomers and tetramers. p63:IA^(g7) (RTRPLWVRME) (SEQ IDNO:5), InsB₁₀₋₂₃:IA^(g7) (HLVERLYLVCGEEG) (SEQ ID NO:9), 2W:IA^(b)(EAWGALANWAVDSA) (SEQ ID NO:8) and LLO:IA^(b) (NEKYAQAYPNVS) (SEQ IDNO:10) was either from the NIH tetramer core facility (Emory University,Atlanta, GA) or produced using S2 insect cell expression system (Moon etal. Nat Protoc 4:565-581 (2009); Moon et al. Immunity 27:203-213 (2007)Pauken et al. J Immunol 191:4913-4917 (2013)). Briefly, peptide:IA^(g7)or peptide:IA^(b) molecules were expressed in Drosophila S2 cells usingthe DES Drosophila Expression System kit (Invitrogen, Carlsbad, CA). TheS2 cells were cotransfected using calcium phosphate, with plasmidsencoding the alpha chain, the peptide-linked beta chain, BirA ligase anda blasticidin resistance gene at a molar ratio of 9:9:9:1 for IA^(b) andIA^(g7). Transfected cells were selected in blasticidin-containingSchneider's Drosophila Medium (Invitrogen, Carlsbad, CA) with 10% fetalbovine serum, 100 Units per milliliter (U/mL) penicillin/streptomycin(Gibco, ThermoFisher Scientific, Waltham, MA), and 20 micrograms permilliliter (m/mL) gentamycin (Invitrogen, Carlsbad, CA) for 1 week at28° C., passaged into serum-free media containing 25 μg/mL blasticidin(Invitrogen, Carlsbad, CA), and scaled to 0.5 liter (L) cultures in 2 Lshaker flasks maintained at 150 rotations per minute (rpm). When celldensities reached 5×10⁶/mL, monomer expression was induced by theaddition of 0.8 millimolar (mM) copper sulfate. Peptide:IA^(b) orIA^(g7) heterodimers were purified from supernatants 8 days later byimmobilized metal ion affinity chromatography using a His-Bindpurification kit (EMD Millipore, Billerica, MA) and eluted using 1 molar(M) imidazole. The biotinylated pMHCII heterodimers in the eluate werethen affinity purified using Monomeric Avidin UltraLink (Pierce,ThermoFisher Scientific, Waltham, MA). Bound peptide:IA^(b) or IA^(g7)molecules were eluted with 2 mM biotin in phosphate buffered saline(PBS) and excess free biotin was removed by centrifugation and 4 washeswith 12 milliliters (mL) PBS using a 30KD cut-off Amicon Ultra-15 filter(EMD Millipore, Billerica, MA). Tetramers were produced by incubatingpMHCII monomers with streptavidin-APC (#PJ27S, Prozyme, Inc., Hayward,CA) or streptavidin-PE (#PJRS27, Prozyme, Inc., Hayward, CA) at a 4:1molar ratio. For the detection of streptavidin (SA) and fluorochromespecific B cells, ALEXA FLUOR 647 (AF647) was conjugated to SA-PE(Prozyme, Inc., Hayward, CA) for 60 minutes at room temperature using anantibody labeling kit (ThermoFisher Scientific, Waltham, MA) and freeAF647 was removed by centrifugation in a 30 kilodalton (KD) molecularweight cut off filter. The concentration was then adjusted to 1 μM PEbased on the absorbance at 565 nanometers (nm) using a nandropspectrophotometer (ThermoFisher Scientific, Waltham, MA). Similarly,SA-APC (Prozyme, Inc., Hayward, CA) was conjugated to DyLight 755 usingan antibody labeling kit (ThermoFisher Scientific, Waltham, MA) and theconcentration was adjusted to 1 μM APC based on the absorbance at 650nm.

Antigen specific B cell enrichment and phenotyping. BALB/c mice wereimmunized with 50 micrograms (μg) total of pMHCII emulsified in completeFreund's adjuvant (CFA, Sigma-Aldrich, St. Louis, MO) subcutaneously inthe flank and in the base of the tail. Seven days post immunizationsingle-cell suspensions from spleen and pooled lymph nodes (inguinal,brachial, cervical, and axillary) were prepared by forcing the tissuethrough a 100 micrometer (μm) cell strainer using the plunger end of a 1mL syringe, washed with RPMI containing 2% fetal bovine serum, andresuspended in 100 microliter (μL) Fc block (2.4G2, 0.05% sodium azide).The cells were next incubated with 5 nanomolar (nM) SA-PE-AF647, andSA-APC-DyLight755 for 10 minutes at 25° C., followed by peptide:MHCIIconjugated PE and APC tetramers at 10 nM for 25 minutes on ice in afinal staining volume of 200 μL. The cells were then washed with 12milliliters (mL) PBS +2% fetal bovine serum, resuspended in 150 mL ofPBS +2% fetal bovine serum, mixed with 25 μL anti-PE and anti-APCMicroBeads (Miltenyi Biotec, Bergisch Gladbach, Germany) and incubatedfor 25 minutes at 4 degrees Celsius (° C.). The cells were then washedwith 12 mL PBS+2% Fetal Bovine Serum (FBS), resuspended in 3 mL PBS +2%FBS and applied to a magnetized LS column (Miltenyi Biotec, BergischGladbach, Germany). The column was washed 3 times with 3 mL PBS +2% FBS,removed from the magnet, and the cells were eluted in 5 mL PBS +2% FBS.All the eluted cells and 1/20^(th) of the flowthrough were thencentrifuged and stained with surface antibodies IgM-PerCp-Cy5.5 (11/41,eBioscience, ThermoFisher Scientific, Waltham, MA), B220-PE-Cy7(RA3-6B2, Tonbo Biosciences, San Diego, CA), CD38-AF700 (90,eBioscience, ThermoFisher Scientific, Waltham, MA), GL7-FITC (GL7,eBioscience, ThermoFisher Scientific, Waltham, MA), IgD-BV786(11-26c.2a, BD Biosciences, Franklin Lakes, NJ), CD11b-BV510 (M1/70, BDBiosciences, Franklin Lakes, NJ), CD11c-BV510 (N418, BioLegend, SanDiego, CA), F4/80-BV510 (BM8, BioLegend, San Diego, CA), CD90.2-BV510(53-2.1, Biolegend, San Diego, CA), Live/Dead Ghost 510 dye (TonboBiosciences, San Diego, CA) for 30 minutes at 4° C. Next, the cells werefixed with Cytofix/Cytoperm solution (BD Biosciences, Franklin Lakes,NJ) for 20 minutes at 4° C., washed twice with permeabilization buffer,and stained with intracellular antibodies IgG (H+L)-AF350 (polyclonal,ThermoFisher Scientific, Waltham, MA) for 30 minutes at 4° C. inpermabilization buffer prior to flow cytometry analysis on a LSRIIFortessa instrument (Becton Dickinson, Franklin Lakes, NJ) equipped with5 laser lines (355 nm, 405 nm, 488 nm, 561 nm, and 640 nm). Allantibodies were used at a 1:100 dilution for staining, except CD90.2which was diluted 1:500. The data were analyzed using FlowJo software(v.10) (FlowJo, LLC, Ashland, Oregon).

Isolation and fusion of antibody producing B cells. BALB/c mice wereimmunized subcutaneously in the flank and in the base of the tail with50 micrograms (μg) of p:MHCII monomer emulsified in complete Freunds'adjuvant. Twenty eight days later each mouse was boosted by intravenousinjection of 100 μL total volume containing 25 μg of p:MHCII in PBS.Three days after boost, mice were euthanized and a single cellssuspension was made from pooled spleens and draining lymph nodes. Cellswere stained in 150 μL of complete media (DMEM, 10% Fetal Calf Serum(FCS), β-ME, pen/strep, nonessential amino acids) containing 13.3 nMPE-conjugated p:MHCII/mouse and incubated on ice for 25 minutes. Cellswere washed with complete media and resuspended in 200 μL of completemedia containing 50 μL of anti-PE microbeads (Miltenyi Biotec, BergischGladbach, Germany)/mouse and incubated on ice for 25 minutes. Cells werewashed with complete media and resuspended in 5 mL of completemedia/spleen. The cell suspension was then applied to a pre-equilibratedLS magnetic column (Miltenyi Biotec, Bergisch Gladbach, Germany) andwashed 2 times with 3 mL of complete media. The cells were eluted fromthe column in 5 mL Medium A (StemCell Technologies, Vancouver, Canada),centrifuged, and enumerated. The enriched B cells were fused with SP2/0mouse myeloma cells using the HY Hybridoma Cloning Kit according themanufacturer's protocol using Method A (StemCell Technologies,Vancouver, Canada). A small portion of the enriched cells and flowthrough was stained as described above to determine antigen specific Bcell purity and phenotype prior to hybridoma fusion.

Hybridoma selection and specificity screening. Twelve dayspost-hypoxanthine-aminopterin-thymidine (HAT) selection, individualcolonies were handpicked and transferred to 96-well plates containingMedium E (StemCell Technologies, Vancouver, Canada). Four days laterhybridoma supernatants were transferred to 96-well plates and freshmedium E was added to the cells. To test the specificity of hybridomasupernatants for MHCII and p:MHCII, a decoy screening approach wasemployed. ELISA plates were coated with 50 nanograms (ng)/well eitherp63:IA^(g7) or InsB₁₀₋₂₃:IA^(g7) (for p63:IA^(g7) antibodies), or2W:IA^(b) or LLO:IA^(b), and then blocked with 1% BSA in PBS for 1 hour.Hybridoma supernatants were mixed 1:1 with ELISA wash buffer (PBS +0.05%Tween20) and added to the p:MHCII coated plates and incubated at 37° C.for 2 hours. Media alone was used as a negative control whileanti-IA^(g7) (clone 10-2.16²⁸, Bio X Cell, West Lebanon, NH) oranti-IA^(b) (Y3P²⁹, ATCC, Manassas, Virginia) were used as a positivecontrol. For antibody detection the wells were incubated with HRPconjugated goat anti-mouse IgG (BioLegend, San Diego, CA) diluted to1:2000 at room temperature for 2 hours followed by addition of ABTSsubstrate solution (KPL, SeraCare Life Sciences, Milford, MA) anddetection by absorbance at 405 nm. Antibodies reacting to both p:MHCIImonomers were considered specific for MHCII independent of peptide,while antibodies reacting with only p63:IA^(g7) or 2W:IA^(b) wereconsidered p:MHCII specific.

Antibody affinity measurements and sequencing. The affinity of the twonovel MAb generated (FS1 and W6) were directly compared with knownIA^(g7) or IA^(b) specific antibodies (10-2.16²⁸ (Bio X Cell, WestLebanon, NH), Y3P²⁹ (ATCC, Manassas, Virginia), Y-Ae³ (eBioscience,ThermoFisher Scientific, Waltham, MA), and AF6-120.1³⁰ (Biolegend, SanDiego, CA)) by Bio-Layer Interferometry by Precision Antibody (Columbia,MD). Antibody sequences were obtained using the SMARTer RACE cDNAAmplification Kit (Clontech, Mountain View, CA) according to themanufactures instructions. Primers used for reverse transcription were

(heavy chain) (SEQ ID NO: 11) GATTACGCCAAGCTTTATGCAAGGCTTACAACCACA,(heavy chain nested) (SEQ ID NO: 12)GATTACGCCAAGCTTCACAATTTTCTTGTCCACCTTGGTGC, (kappa light chain)(SEQ ID NO: 13) GATTACGCCAAGCTTCTCATTCCTGTTGAAGCTCTTGACAAT,(lambda light chain 1, 4) (SEQ ID NO: 14)GATTACGCCAAGCTTACACTCAGCACGGGACAAACTCTTCTC, (lambda 2,3) (SEQ ID NO: 15)GATTACGCCAAGCTTACACTCTGCAGGAGACAGACTCTTTTC.

Proliferation and cytokine production. Cells were isolated from spleenand peripheral lymph nodes of NOD.BDC2.5 transgenic mice, the red bloodcells were lysed by Tris-buffered ammonium chloride, and the cells werelabeled with CFSE (ThermoFisher Scientific, Waltham, MA). Labeled cellswere resuspended in complete DMEM media at a final concentration of4×10⁶ cells/mL and p63 or p31 peptide was added to a final concentrationof 0.05 μM. Purified monoclonal antibody or 50 μL of hybridomasupernatant was added to each well containing 200 μL of cells in a96-well plate, and incubated for 4 days at 37° C. with 5% CO₂. Cellswere harvested, resuspended in 2.4G2 Fc block for 10 minutes at 4° C.,and stained at 1:100 dilution for 30 minutes at 4° C. with antibodiesagainst CD4-BV510 (RM4-5, BD Biosciences, Franklin Lakes, NJ),CD8α-BV650 (53-6.7, BD Biosciences, Franklin Lakes, NJ),CD3e-PerCp-Cy5.5 (KT4, BD Biosciences, Franklin Lakes, NJ), B220-ef450(RA3-6B2, eBioscience, ThermoFisher Scientific, Waltham, MA),CD11c-ef450 (N418, eBioscience, ThermoFisher Scientific, Waltham, MA),CD11b-ef450 (M1/70, eBioscience, ThermoFisher Scientific, Waltham, MA),T cell receptor (TCR) Vβ4-PE (KT4, BD Biosciences, Franklin Lakes, NJ)and dead cells were gated out using a viability ghost red dye (TonboBiosciences, San Diego, CA), and run on a LSRII Fortessa X-20 flowcytometer (Becton Dickinson, Franklin Lakes, NJ) and analyzed usingFlowJo software (v10). For antibody dose response curves, cells wereisolated from NOD.BDC2.5 transgenic mice, labeled with CFSE as describedabove, and cultured with p31 or p63 (0.05 μM) with varying doses of FS1MAb, or isotype control (Bio X Cell, West Lebanon, NH). After a 4 dayincubation at 37° C. with 5% CO₂, cells were harvested for flowcytometry, while supernatants were analyzed using ProcartaPlex Assay kitEPX170-26087-901 (eBioscience, ThermoFisher Scientific, Waltham, MA).

Antibody staining of peptide pulsed antigen presenting cells. Purifiedmonoclonal antibody was directly conjugated to Alexa Fluor-488 (AF488)by protein labeling kit (ThermoFisher Scientific, Waltham, MA) accordingto the manufacturer's protocol. Splenocytes were isolated from NOD mice,red blood cells (RBCs) lysed, and resuspended at in complete DMEM at6×10⁶ cells/mL. p63 or OVA₁₄₁₋₁₆₀ was added to the media at a finalconcentration of 40 μM and the cells were incubated for 1.5 hours at 37°C. with 5% CO₂. Cells were harvested incubated in 2.4G2 for 10 minuteson ice and stained at 1:100 dilution for 30 minutes at 4° C. withFS1-AF488 and antibodies against CD4-BUV395 (GK1.5, BD Biosciences,Franklin Lakes, NJ), CD8α-APC-ef780 (53-6.7, eBioscience, ThermoFisherScientific, Waltham, MA), CD3ε-BV650 (145-2C11, BD Biosciences), B220-PE(RA3-6B, Tonbo Biosciences, San Diego, CA), CD11c-PE-Cy (N418,eBioscience, ThermoFisher Scientific, Waltham, MA), CD11b-PerCp-Cy5.5(M1/70, Tonbo Biosciences, San Diego, CA), F4/80-APC (BM8.1, TonboBiosciences, San Diego, CA), IA^(g7)-biotin (10.2-16, Bio X Cell, WestLebanon, NH), SA-BV421 (Biolegend, San Diego, CA) and dead cells weregated out using GHOST DYE Violet 510 (Tonbo Biosciences, San Diego, CA),and run on a LSRII Fortessa X-20 flow cytometer (Becton Dickinson,Franklin Lakes, NJ) and analyzed using FlowJo software (v10).

In vivo blockade of T cell activation. NOD mice were administered 50micrograms (m) acetylated-p63 peptide with either 250 μg FS1 or Y-Ae MAbin PBS containing 2 μg lipopolysaccharide (Sigma-Aldrich, St. Louis, MO)by intravenous injection in the tail vein. Four days post-injection micewere euthanized and splenocytes were isolated and RBCs lysed as above.Cells were stained with both APC and PE-conjugated p63:IA^(g7) tetramersfollowed by magnetic enrichment of double tetramer positive cells aspreviously described (Pauken et al. J Immunol 191:4913-4917 (2013); Tuboet al. Cell 153:785-796 (2013)). Enriched cells were incubated with2.4G2 Fc block for 10 minutes at 4° C. and stained with surfaceantibodies at 1:100 dilution for 30 minutes at 4° C. againstCD3e-APC-ef780 (17A2, eBioscience, ThermoFisher Scientific, Waltham,MA), CD4-BUV395 (GK1.5, BD Biosciences, Franklin Lakes, NJ), CD8α-BV650(53-6.7, BD), CD44-BV786 (IM7, BD Biosciences, Franklin Lakes, NJ),B220-PerCp-Cy5.5 (RA3-6B2, eBioscience, ThermoFisher Scientific,Waltham, MA), CD11b-PerCp-Cy5.5 (M1/70, Tonbo Biosciences, San Diego,CA), CD11c-PerCp-Cy5.5 (N418, eBioscience, ThermoFisher Scientific,Waltham, MA), and GHOST DYE Violet 510 (Tonbo Biosciences, San Diego,CA) for 30 minutes at 4° C. The cells were then fixed using the Foxp3staining buffer kit (eBioscience, ThermoFisher Scientific, Waltham, MA)and stained with anti-Ki67-PE-Cy7 (SolA15, eBioscience, ThermoFisherScientific, Waltham, MA) antibodies for 1 hour at 4° C., and run on aLSRII Fortessa X-20 flow cytometer (Becton Dickinson, Franklin Lakes,NJ) and analyzed using FlowJo software (v10).

Infections. C57BL/6 mice were injected intravenously with 10⁷actA-deficient Listeria monocytogenes expressing 2W protein (Ertelt etal. J Immunol 182:3032-3038 (2009)) and on the same day injectedintravenously with 500 μg of W6 (anti-2W:IA^(b)) blocking antibody.Seven days later, splenocytes were isolated, and stained as above andmagnetically enriched for 2W:IA^(b)-PE tetramer. Cells were run on aLSRII Fortessa X-20 flow cytometer (Becton Dickinson, Franklin Lakes,NJ) and analyzed using FlowJo software (v10).

Foot pad immunization, antigen presenting cell isolation and staining.NOD hind limb foot pads were injected with 100 μL total volumecontaining 200 μg of p63 or OVA₁₄₁₋₁₆₀ peptide in PBS. One and halfhours later the popliteal lymph nodes were removed, minced, and digestedin RPMI containing 2% FCS, collagenase D (40 U/mL), and DNase I (250μg/mL) for 30 minutes at 4° C. Cells were then washed with Hanksbalanced salt solution containing 5 mM EDTA and 2% FCS, centrifuged, andstained with surface antibodies and analyzed by flow cytometry asdescribed above using the FS1 AF488 antibody.

Ear pinna immunization, antigen presenting cell isolation and staining.C57BL/6 mice were immunized intradermally in the ear pinna with 10 μgeither Ovalbumin (OVA) or 2W-GFP plus 1 μg double mutant labile toxin(Norton et al. Vaccine 33:1909-1915 (2015)) or 10 μg CpG (Sigma-Aldrich,St. Louis, MO). After 24 hours, the cervical lymph nodes were removed,dissociated using a 100-micron mesh and mechanically disrupted, anddigested with 300 Mandl U/mL Collagenase D (Roche Applied Sciences) for30 minutes at 37° C. in 1×PBS +2% FBS. Cells were then washed 1×PBS +2%FBS, centrifuged, and Fc receptors were blocked in 100 μL 2.4G2hybridoma supernatant containing 2% rat and mouse serum for 10 minutesat room temperature. For surface staining, 1 μg of biotinylated W6antibody was added to the cells and incubated on ice for 45 minutes,washed with PBS +2% FCS, followed by staining for 30 minutes at 4° C.with antibodies CD11c-PerCpCy5.5 (N418, BioLegend, San Diego, CA),CD11b-AF700 (M1/70, BioLegend, San Diego, CA), CD19-ef450 (1D3,eBioscience, ThermoFisher Scientific, Waltham, MA), MHCII-FITC(M5/114.15.2, BioLegend, San Diego, CA), DEC-205-PE (205yekta,eBioscience, ThermoFisher Scientific, Waltham, MA), and streptavidin-APC(BioLegend, San Diego, CA). All antibodies were used at 1:100 dilutionexcept CD11c and CD19 were used at 1:40 and CD11b was used at 1:200. Thecells were then run on a LSRII flow cytometer (Becton Dickinson,Franklin Lakes, NJ) and analyzed using FlowJo software (v10).

Statistical Analysis. Data display and statistical analysis wasconducted using Prism software (GraphPad Prism v6, GraphPad Software,San Diego, CA). Statistical significance was analyzed using thetwo-tailed Student's t-test for comparison of two mean. Values of p≤0.05were considered significant.

Sequence availability. Sequence data that support the findings of thisstudy have been deposited in GenBank with the primary accession codes:FS1 Heavy chain KU955585 (available on the world wide web atncbi.nlm.nih.gov/nuccore/KU955585), FS1 Light chain KU955586 (availableon the world wide web at ncbi.nlm.nih.gov/nuccore/KU955586), W6 Heavychain KU955587 (available on the world wide web atncbi.nlm.nih.gov/nuccore/KU955587), and W6 Light chain KU955588(available on the world wide web at ncbi.nlm.nih.gov/nuccore/KU955588).

Results

The workflow and the necessary steps for p:MHCII MAb generation asdescribed in this Example are illustrated in FIG. 1 . Generation andvalidation of p:MHCII MAb can be completed in less than 8 weeks. Todevelop a reagent to block T cell receptor (TCR) recognition of adiabetes-relevant peptide, antibodies against p63 peptide in the contextof IA^(g7) MHC II molecule were initially developed, given thatp63-activated BDC2.5 CD4⁺ T cells mediate accelerated autoimmunediabetes when transferred into wild type non-obese diabetic (NOD) hosts.Splenocytes from five p:MHCII (p63:IA^(g7)) immunized BALB/c mice wereisolated and magnetically enriched for antigen specific B cells using PEconjugated p63:IA^(g7) tetramers followed by anti-PE magnetic beads(Pape et al. Science 331:1203-1207 (2011)) To validate successfulpriming and expansion, the phenotype of p:MHCII-specific B cells wasanalyzed in naïve mice compared to day 7 post immunization (FIG. 7A).Antigen-specific B cells were identified by p:MHCII tetramer excludingthose that bound to SA-PE or SA-APC using SA-PE-AF647 or SA-APC-DyLight755 from immunized mice, compared to a decoy p:MHCII reagent (FIG. 7A).Three distinct subsets of antigen-specific B cells (p:MHCII specific,MHCII specific, and decoy p:MHCII specific) (Pape et al. Science331:1203-1207 (2011); Taylor et al. J Exp Med 209:2065-2077 (2012)) wereevaluated for GL7 and intracellular Ig expression associated with maturegerminal center B cells. Phenotypic analysis demonstrates thep:MHCII-PE⁺ population is enriched for mature germinal center B cells(GL7⁺ and intracellular Ig⁻) demonstrating successful priming and T cellhelp (FIG. 7A). The enrichment approach at day 3 post antigen boost wasverified, prior to hybridoma fusion. Magnetic enrichment resulted in anincrease to 11.1% of the B cells staining positive for p63:IA^(g7)-PEtetramer, and phenotypic markers demonstrating the presence of germinalcenter B cells within this population (FIG. 7B). The enriched fractioncontained 2.1×10⁷ cells, a 23-fold reduced compared to the startingpopulation. These cells were subsequently fused with SP2/0 myeloma cellsand plated onto ten 100 millimeter (mm) plates containing semi-solidmedia under hypoxanthine-aminopterin-thymidine (HAT) selection. Fourteendays after plating, 190 colonies were picked and screened by ELISA.Without enrichment, 50 plates would have been required to screen 5×10⁸cells, and these 50 plates likely would have contained at least 5000colonies, most of which could not have been selected or screened forfurther analysis due to time and reagent constraints. Thus, enrichmentallowed screening of every visible colony and saved significant time andreagents.

After expansion of each colony, secreted antibody in the culturesupernatant was assessed for binding to p63:IA^(g7) compared to decoyInsB₁₀₋₂₃:IA^(g7) by ELISA. Thirty-two of the 190 colonies producedantibodies that bound to both p63:IA^(g7) and InsB₁₀₋₂₃:IA^(g7),indicating specificity for an IA^(g7) epitope (Table 1).

TABLE 1 Efficiency of generating hybridomas producing p:MHCII specificantibodies #Hybridomas #Hybridomas⁺ (%)* #Hybridomas⁺ Antigen # Miceimmunized screened for MHCII for peptide:MHCII (%) p63:IA^(g7) 5 190  32(16.8) 11 (5.8)⁺ 2W:IA^(b) 2 576 234 (40.6)  5 (0.9)⁺ LLO:IA^(b) 2 576236 (40.9) 32 (13.5)* Ins:IA^(g7) 2 576  22 (3.8) 11 (1.9)* p31:1A^(g7)2 480  21 (4.4) 14 (2.9)* mimetope:IA^(g7) 2 480  21 (4.4) 12 (2.5)**Specificity as defined by functional assay blocking T cellproliferation or MAb binding to APCs. ^(§)Specificity as defined bypositive ELISA plate compared to decoy pMHCII complex.

In contrast, 11 hybridomas produced antibodies that bound onlyp63:IA^(g7) (34.4% success rate for p:MHC or 5.8% overall), suggestingthe desired specificity for this peptide bound to IA^(g7) (Table 1).FIG. 8A illustrates twenty clones, ten that reacted to both p63:IA^(g7)and InsB₁₀₋₂₃:IA^(g7), and ten that are unique for p63:IA^(g7). The 10clones that uniquely bound p63:IA^(g7) were further characterized forTCR blocking ability to limit in vitro antigen specific T cellproliferation (FIG. 8B). Splenocytes were isolated from TCR transgenicBDC2.5 mice, labeled with carboxyfluorescin (CFSE) and cultured with p63peptide in the presence or absence of hybridoma supernatant for fourdays. BDC2.5 splenocytes incubated with peptide only resulted in 87.5%CD4⁺ T cells proliferating, while T cells incubated with peptide plushybridoma A1 limited BDC2.5 T cell proliferation to 56% (FIG. 8B). Theremaining 9 hybridomas screened had varying degrees of inhibition (FIG.8B). An isotype specific ELISA was then used to determine that A1antibody was IgG1.

A large scale purification was performed to obtain purified MAb fromhybridoma A1 (named FS1). Using the FS1 MAb (anti-p63:IA^(g7)) an invitro dose response assay was performed an 80.5% specific reduction inproliferation was demonstrated with 1.72 μM FS1 MAb (FIG. 8C). Incontrast, the FS1 MAb only reduced BDC2.5 T cell proliferation toanother BDC2.5 mimetope (p31) by 5.6% compared to isotype control (FIG.3C). p63-activated BDC2.5 T cells demonstrated 99.85% reduction in IFNγproduction when cultured with 1.7204 of FS1 MAb, compared to isotypecontrol (FIG. 8C). Importantly, IFNγ production by p31-activated BDC2.5T cells was not altered (FIG. 8C). A similar trend with IL-17A was noted(FIG. 3C). Taken together, these findings illustrate the specificity ofthe FS1 MAb as p31 differs from p63 by two amino acids at positions P-1and P1 of the MHCII binding pocket (Judkowski et al. J Immunol166:908-917 (2001)). As an extension of specific binding, splenocytesfrom NOD mice were p63 peptide pulsed and stained with labeled FS1 MAbillustrating CD8a conventional dendritic cells (cDCs) and B220+B cellsstained positive for p63 peptide but not ovalbumin peptide (OVA₁₄₁₋₁₆₀)control (FIG. 8D). The uniform histogram shift suggests a large portionof the DCs and B cells stained with varying levels of FS1 MAbdemonstrating peptide presentation in vitro (FIG. 8D). CD4⁺ and CD8⁺ Tcells did not stain positive for the FS1 MAb (FIG. 8D). Immunostainingwas next performed to demonstrate peptide binding to MHCII in vivo. NODmice were injected with p63 or OVA peptide in the footpad and 1.5 hourslater popliteal lymph node cells were stained with FS1 antibody toidentify p63 loaded antigen presenting cells (FIG. 8E). Both DCs and Bcells had significantly increased FS1 MAb staining in response to p63peptide pulsed compared to OVA peptide (p=0.005 and p=0.008,respectively), while T cells showed no specific staining (FIG. 8E).

Using this methodology, an antibody specific for the peptide 2W was alsogenerated (Moon et al. Nat Protoc 4:565-581 (2009); Rees et al. ProcNatl Acad Sci USA 96:9781-9786 (1999)) bound to IA^(b) (named W6). Usingthis reagent, in vitro antigen loading and presentation were validatedusing bone marrow derived dendritic cells that were pulsed with greenfluorescent protein (GFP)-linked 2W peptide. Results in FIG. 9Ademonstrate that 47% of the GFP positive cells were W6 MAb(anti-2W:IA^(b)) positive and were mostly CD11c⁺CD11b⁺ double positivecells. In vivo antigen loading and presentation were also validated.C57BL/6 mice were immunized intra-dermally with either ovalbumin proteinor 2W-GFP. At 24 hours post injection, MHCII antigen presenting cellsfrom the draining lymph node had increased W6 MAb reactive populations(15%) compared to 1% of controls (FIG. 9B). In a separate in vivo model,the W6 MAb was used to identify antigen presenting cells immunized withtwo different adjuvants. C57BL/6 mice were immunized with 2W-GFP andeither 5′-cytosine-phosphate-guanine-3′ (CpG) or double-mutantheat-labile toxin (dmLT) (Norton et al. Vaccine 33:1909-1915 (2015)).Twenty-four hours later, draining lymph nodes were assayed by flowcytometry for antigen-specific presentation using the W6 antibody. Shownin FIG. 9C, the W6 MAb identified 27% of the DCs containing GFP comparedto 3% in the isotype control group and all these cells wereCD11b⁺CD11c⁺CD19⁻ dendritic cells. These results demonstrate that W6 MAbcan identify different subsets of antigen presenting cells in vivo.

Next, whether MAbs directed against p:MHCII could prevent TCRrecognition in vivo to limit T cell proliferation was determined. NODmice were challenged with p63 peptide plus lipopolysaccharide (LPS) withFS1 MAb or Y-Ae³ (anti-Eα:IA^(b)) as a negative control. Four days postchallenge a significant reduction in antigen specific T cell expansionwith FS1 MAb administration was measured (FIG. 10A). Using dualfluorochrome tetramer staining and flow cytometry, 30-fold expansion ofp63 specific T cells stimulated with p63+LPS+Y-Ae MAb control, comparedto only a 2-fold expansion with p63+LPS+FS1 MAb over naïve cells wasdetected (FIG. 10A). In addition to decreased expansion, the FS1 MAb wasobserved to decrease activation and cell cycle progression (FIG. 10A).Next, the FS1 MAb was used in vivo to prevent antigen specifictolerance, resulting in rapid autoimmune diabetes. Specifically,activated BDC2.5 T cells were transferred after 4 days in vitrostimulation into wild-type NOD pre-diabetic recipients followed byinjection of ethelyene-carbodiimide (ECDI) fixed p63-peptide coupledcells (p63cc) to induce tolerance (Pauken et al. J Immunol 191:4913-4917(2013); Pauken et al. Diabetes 62:2859-2869 (2013)) and either controlor FS1 MAb and monitored the mice for diabetes. p63cc completelyprevented diabetes induction in 100% of the mice, while control bovineserum albumin coupled cells (BSAcc)-treated mice develop severe diabetes(FIG. 10B). Mice given p63cc and FS1 MAb developed diabetes, indicatingthe FS1 MAb prevented the induction of antigen specific tolerance invivo.

The W6 MAb was next evaluated for its ability to block 2W specific invivo expansion of antigen specific T cells in response to an acute orchronic bacterial infection. C57BL/6 mice were administered W6 MAb andinfected with Listeria monocytogenes expressing 2W (Ertelt et al. JImmunol 182:3032-3038 (2009)). Seven days later, the number of activated2W specific cells was decreased by 146 fold in response to W6 MAbcompared to no antibody control (FIG. 11A). To test in vivo 2W specificCD4⁺ T cell responses and their contribution to bacterial clearance in achronic infection, 129 mice were infected with 10⁸ Salmonellatyphimurium expressing 2W peptide (Uzzau et al. Proc Natl Acad Sci USA98:15264-15269 (2001); Nelson et al. J Immunol 190:2828-2834 (2013)).The mice received a single dose of W6 blocking antibody fourteen dayspost infection and were sacrificed at day 35 to evaluate antigenspecific T cell proliferation and colony forming units (CFU). Infectedmice treated with the W6 MAb have significantly lower 2W specific CD4⁺ Tcells, higher bacterial burden, and do not clear the salmonellainfection (FIG. 11B and FIG. 11C). These data highlight the importanceof a single antigen-specific T cell population and the blocking abilityof the W6 MAb to prevent in vivo pathogen clearance.

To compare the affinity of the FS1 and W6 MAb with previously publishedreagents, a direct side-by-side comparison with known IA^(g7) or IA^(b)specific antibodies was performed. The results are shown in Table 2, andillustrate that the FS1 MAb (anti-p63:IA^(g7)) has 100 fold higheraffinity (1.7×10⁻¹¹) than the 10-2.16 MAb28 (anti-IA^(g7)) (2.9×10⁻⁹K_(D) (M)). The W6 MAb (anti-2W:IA^(b)) had an affinity comparable toknown IA^(b) antibodies (Y3P²⁹, Y-Ae³, and AF6-120.1³⁰). These resultssuggest that the two MAb generated had comparable or higher affinitythan conventional approaches used to develop MAb.

TABLE 2 Comparison of anti-p:MHCII antibody affinities Antibody cloneAntigen K_(D)(M) FS1 p63:IA^(g7) 1.7 × 10⁻¹¹ 10-2.16 (ref. 28)p63:IA^(g7) 2.9 × 10⁻⁹ W6 2W:IA^(b) 3.4 × 10⁻⁹ AF6-120.1 (ref. 30)2W:IA^(b) 7.1 × 10⁻⁹ Y3P (ref. 29) 2W:1A^(b) 1.9 × 10⁻⁹ Y-Ae (ref. 3) Eα

₂₋₆₈:IA^(b) 4.8 × 10⁻¹⁰

indicates data missing or illegible when filed

Discussion

Using this methodology hybridomas producing six novel anti-peptide:MHCIIMAb were generated, and for two of these presented here, the highaffinity and biological capacity to limit TCR engagement, preventsubsequent T cell activation, label antigen presenting cells, and invivo use to prevent tolerance induction and bacterial pathogen clearancewere demonstrate. This novel methodology is highly efficient in part dueto pre-screening and enrichment, saving both time and resources (see,e.g., Table 1).

Recently, an antibody against insulin B peptide₉₋₂₃ in IA^(g7)(anti-InsB₉₋₂₃:IA^(g7)) was generated and shown to inhibit diabetes inNOD mice (Zhang, L. et al. Proc Natl Acad Sci USA 111, 2656-2661(2014)). In the current study, the FS1 MAb was generated as a diabetesrelevant peptide in the context of IA^(g7). Here, successful blockade ofantigen specific tolerance using FS1 MAb and rapid diabetes weredemonstrate (FIG. 10B). The W6 reagent was generated to understand Tcell responses during both homeostasis and bacterial pathogenesis, asthe 2W peptide can be engineered into a pathogen of interest.

Example 3

Except as otherwise indicated, the reagents used in Example 3 wereobtained from the same source as the reagents in Example 2 and themethods of Example 3 are as further described in Example 2.

Three C57BL/6 mice were immunized with phycoerythrin (PE) (Prozyme,Hayward, CA) by subcutaneous injection of 100 μL of complete Freund'sadjuvant (CFA) (Sigma-Aldrich, St. Louis, MO) emulsion containing 25 μgof PE in the hind flank. After 3 weeks, mice were boosted intravenouslywith 50 μg of PE. Three days later, the spleen and pooled lymph nodes(inguinal, brachial, cervical, and axillary) were harvested. Single-cellsuspensions from spleen and pooled lymph nodes (inguinal, brachial,cervical and axillary) were prepared by forcing the tissue through a 100μm cell strainer using the plunger end of a 1 mL syringe, washed withRPMI containing 2% FBS and resuspended in 100 μL with RPMI containing 2%FBS. The cells were next incubated with 1 μg PE to each sample (spleenand pooled lymph nodes per mouse for 30 min at 4° C., followed by 25 μLanti-PE microbeads (Miltenyi Biotec, Bergisch Gladbach, Germany) andincubated for 15 min at 4° C. The cells were then washed with 12 mL withPBS 2% FBS, resuspended in 3 mL PBS with 2% FBS and applied to amagnetized LS column (Miltenyi Biotec, Bergisch Gladbach, Germany). Thecolumn was washed three times with 3 mL PBS with 2% FBS, removed fromthe magnet and the cells were eluted in 5 mL PBS with 2% FBS. Themagnetically labeled cells were pelleted and re-suspended in 100 μL PBSwith 2% BSA followed by staining with BRILLIANT violet 421(BV421)-anti-CD138 (a plasma cell marker), BV650-anti-B220 (a B cellmarker), GHOST DYE Violet 510 (a viability marker), and BRILLIANT violet510 (BV510)-anti-CD90.2, anti-CD11c, anti-F4/80, and anti-GR-1 (FIGS.12-13 ). PE-specific cells were determined by negative staining using adump gate to exclude T cells (CD90), macrophage (F4/80), dendritic cells(CD11c) and granulocytes (GR-1). B220 intermediate B cells or B220 highB cells or CD138 positive and PE positive cells were sorted on a BDFACSAria II. Approximately 400,000 PE-specific B cells were obtainedwith 98% purity (FIG. 12 ). All antibodies were used at a 1:100 dilutionfor staining, except CD90.2 which was diluted 1:500. The data wereanalyzed using FlowJo software (v.10) (FlowJo, LLC, Ashland, Oregon).

The enriched B cells were fused with SP2/0 mouse myeloma cells using theHY Hybridoma Cloning Kit according the manufacturer's protocol usingmethod A (Stem Cell Technologies, Vancouver, Canada) and plated out intosemi-solid methylcellulose-based HAT media as described in Example 2.Fourteen days later, 5 visible colonies were harvested from the platesand grown in hypoxanthine-thymidine (HT) containing media until ELISAscreening.

Supernatants from each hybridoma clone were screened for PE binding viaindirect ELISA. Supernatant was incubated in a 96-well plate previouslycoated with 20 μg/mL PE and blocked with 1% BSA. PE binding antibodieswere detected by incubating with HRP-conjugated goat anti-mouse IgG(BioLegend, San Diego, CA) diluted to 1:2000 at room temperature for 45minutes followed by addition of ABTS substrate solution (KPL, SeraCareLife Sciences, Milford, MA) and detection by absorbance at 405 nm.Results are shown in FIG. 14 . Sequences for Clones 1, 4, and 5 areshown in FIG. 23 . The sequences for Clone 1 and Clone 2 are the same.

Example 4

Except as otherwise indicated, the reagents used in Example 4 wereobtained from the same source as the reagents in Example 2 and themethods of Example 4 are as further described in Example 2.

Mice were immunized according to the immunization scheme shown in FIG.15 . Two modified IA^(g7) MHCII monomers containing the insulin peptides(InsB p8E, InsB p8G) shown in FIG. 16 were used to make a cross-reactivemonoclonal antibody. Two BALB/c mice were immunized subcutaneously inthe flank and base of the tail with 50 μg total of Ins p8E:IA^(g7) MHCIImonomer emulsified in complete Freunds' adjuvant. Twenty eight dayslater each mouse was boosted by intravenous injection of 100 μL totalvolume containing 10 μg of Ins p8G:IA^(g7) MHCII monomer in PBS.Fourteen days later (day 42) each mouse was boosted by intravenousinjection of 100 μL total volume containing 10 μg of Ins p8G:IA^(g7) inPBS. Three days after the second boost (day 45), mice were euthanizedand a single cell suspension was made from cells from pooled spleens anddraining lymph nodes. Cells were stained in 150 μL of complete media(DMEM, 10% Fetal Calf Serum (FCS), β-ME, pen/strep, nonessential aminoacids) containing 13.3 nM PE-conjugated p:MHCII/mouse and incubated onice for 25 minutes. Cells were washed with complete media andresuspended in 200 μL of complete media containing 50 μL of anti-PEmicrobeads (Miltenyi Biotec, Bergisch Gladbach, Germany) per mouse andincubated on ice for 25 minutes. Cells were washed with complete mediaand resuspended in 5 mL of complete media per spleen. The cellsuspension was then applied to a pre-equilibrated LS magnetic column(Miltenyi Biotec, Bergisch Gladbach, Germany) and washed 2 times with 3mL of complete media. The cells were eluted from the column in 5 mLMedium A (StemCell Technologies, Vancouver, Canada), centrifuged, andenumerated. The enriched B cells were fused with SP2/0 mouse myelomacells using the HY Hybridoma Cloning Kit according the manufacturer'sprotocol using Method A (StemCell Technologies, Vancouver, Canada). Asmall portion of the enriched cells and flow through was stained asdescribed in Example 2 to determine antigen specific B cell purity andphenotype prior to hybridoma fusion.

Hybridoma selection and specificity screening. Twelve dayspost-hypoxanthine-aminopterin-thymidine (HAT) selection, 624 individualcolonies were handpicked and transferred to 96-well plates containingMedium E (StemCell Technologies, Vancouver, Canada). Four days laterhybridoma supernatants were transferred to 96-well plates and freshmedium E was added to the cells. To test the specificity of hybridomasupernatants for MHCII and p:MHCII, a decoy screening approach wasemployed. ELISA plates were coated with 50 nanograms (ng)/well eitherHEL₁₁₋₂₅:IA^(g7) or Ins p8E:IA^(g7), or Ins p8G:IA^(g7), and thenblocked with 1% BSA in PBS for 1 hour. Hybridoma supernatants were mixed1:1 with ELISA wash buffer (PBS +0.05% Tween20) and added to the p:MHCIIcoated plates and incubated at 37° C. for 2 hours. Media alone was usedas a negative control while anti-TAO (clone 10-2.16, Bio X Cell, WestLebanon, NH) was used as a positive control. For antibody detection thewells were incubated with HRP conjugated goat anti-mouse IgG (BioLegend,San Diego, CA) diluted to 1:2000 at room temperature for 2 hoursfollowed by addition of ABTS substrate solution (KPL, SeraCare LifeSciences, Milford, MA) and detection by absorbance at 405 nm. 38 cloneswere determined to be positive for P8E specificity (˜6.1% efficiency),and of these 9 were cross reactive to P8E and PBG. Antibodies reactingto P8E and HEL p:MHCII monomers were considered specific for MHCIIindependent of peptide, while antibodies reacting with Ins p8E:IA^(g7)and Ins p8G:IA^(g7) were considered insulin B 9-23 cross reactive.

In vitro validation. One clone, Ins 4G8, was selected for furtheranalysis (monoclonal antibodies produced by Ins 4G8 are referred toherein as cross reactive insulin 1 (XRI1)); sequence information for theantibody is provided in FIGS. 21-22 ). In vitro staining of Ins 4G8hybridoma with IA^(g7) tetramers. Tetramer validation is shown in FIG.17 . As shown in FIG. 18 , Ins 4G8 hybridomas bind both InsB p8E:IA^(g7)and InsB p8G:IA^(g7) tetramers but not HEL:IA^(g7) or hCLIP:IA^(g7).

In vitro staining of peptide pulsed bone marrow derived dendritic cells(BMDCs) with XRI1 directly conjugated to AF647. Bone marrow washarvested from NOD mice and cultured for 9 days in 20 ng/mL GM-CSF.BMDCs were pulsed overnight with 40 μM peptide or no peptide+1 μg/mL LPSand then stained with AF-647-XRI1. As shown in FIG. 19 , B6.G7 BMDCswere pulsed with InsB p8E, InsB p8G, OVA323-339 or p63 and geometricmean (gMFI) of AF647-XRI1 staining was determined; BMDCs from NOD, B6,B6.G7 and NOD IA^(g7) CIITA KO or NOD CIITA^(−/−)β2M^(−/−) mice werepulsed with InsB p8E and and gMFI was determined.

In vivo validation. FIG. 20 shows in vivo validation of XRI1.

The complete disclosure of all patents, patent applications, andpublications, and electronically available material (including, forinstance, nucleotide sequence submissions in, e.g., GenBank and RefSeq,and amino acid sequence submissions in, e.g., SwissProt, PIR, PRF, PDB,and translations from annotated coding regions in GenBank and RefSeq)cited herein are incorporated by reference. In the event that anyinconsistency exists between the disclosure of the present applicationand the disclosure(s) of any document incorporated herein by reference,the disclosure of the present application shall govern. The foregoingdetailed description and examples have been given for clarity ofunderstanding only. No unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed, for variations obvious to one skilled in the art will beincluded within the invention defined by the claims.

What is claimed is:
 1. A method comprising: immunizing a subject with acomposition comprising an antigen, wherein the antigen comprises apeptide-MHC complex (p:MHC); isolating a population of cells from thesubject; enriching a subpopulation of cells from the population ofcells, wherein enriching a subpopulation of cells comprises excludingcells that do not bind to p:MHC, and wherein enriching a subpopulationof cells further comprises at least one of increasing the proportion ofB cells in the population that bind the antigen, identifying expressionof a lymphocyte marker, identifying mononuclear cells, identifyingexpression of a B cell marker, testing for viability, and testing forantigen specificity; and forming a hybridoma from a cell selected fromthe subpopulation of cells.
 2. The method of claim 1, the method furthercomprising screening the hybridoma for production of an antibodyspecific for the p:MHC.
 3. The method of claim 1 wherein the antigencomprises a monomeric peptide-MHC complex.
 4. The method of claim 1wherein the antigen comprises a peptide-MHC Class I complex (p:MHCI) ora peptide-MHC Class II complex (p:MHCII).
 5. The method of claim 1wherein the antigen comprises at least two peptide-MHC complexes,wherein the MHC of each peptide-MHC complex comprises the same MHC andwherein the peptide of each peptide-MHC complex is different.
 6. Themethod of claim 5 wherein the method comprises immunizing a subject witha composition comprising an antigen comprising one peptide-MHC complexand subsequently immunizing the subject with a composition comprising anantigen comprising another peptide-MHC complex.
 7. The method of claim 1wherein enriching the subpopulation of cells comprises enriching asubpopulation of cells capable of binding to a multimeric form of theantigen.
 8. The method of claim 7 wherein the multimeric form of theantigen comprises at least one of a biotin, a desthiobiotin, and afluorescent biotin derivative.
 9. The method of claim 7 wherein amultimeric form of the antigen comprises at least one of a marker and aphotosynthetic pigment, and wherein excluding cells that do not bind top:MHC comprises excluding cells that bind to the marker or thephotosynthetic pigment.
 10. The method of claim 7 wherein enrichingcells capable of binding to a multimeric form of the antigen comprisesusing a magnetic bead, wherein the magnetic bead binds to at least oneof a marker and a photosynthetic pigment.
 11. The method of claim 1wherein enriching a subpopulation of cells comprises excluding cellsthat bind to a second peptide-MHC complex, wherein the secondpeptide-MHC complex comprises the same MHC complex as the p:MHC of theantigen used to immunize the subject, and further wherein the secondpeptide-MHC complex comprises a different peptide than the p:MHC of theantigen used to immunize the subject.
 12. The method of claim 1 whereinenriching the subpopulation of the cells comprises using flow cytometricidentification and/or sorting.
 14. The method of claim 1, whereinexcluding cells that do not bind to p:MHC comprises excluding cells thatbind to a peptide not bound to an MHC complex and/or to an MHC complexnot bound to a peptide.
 15. The method of claim 1 wherein the subject isa mammal.
 16. The method of claim 1 wherein the subject is a mouse, ahumanized mouse, a rat or a rabbit.
 17. The method of claim 1 whereinthe composition comprising an antigen further comprises an adjuvant. 18.The method of claim 17, wherein excluding cells that do not bind top:MHC comprises excluding cells that bind to the adjuvant.
 19. Amonoclonal antibody, wherein the monoclonal antibody comprises at leastone of: a heavy chain variable region of FS1, W6, XRI1, or FIG. 23 and alight chain variable region of FS1, W6, XRI1, or FIG. 23 .
 20. Amonoclonal antibody, wherein the monoclonal antibody comprises at leastone of: a heavy chain variable region comprising a complementaritydetermining region (CDR) of the heavy chain of FS1, W6, XRI1, or FIG.
 23. a light chain variable region comprising a complementarity determiningregion (CDR) of the light chain of FS1, W6, XRI1, or FIG. 23 .